A STUDY OF THE KINETICS OF THE GASEOUS
REACTION OF TRIMETHYLBORANE AND OXYGEN
DISSERTATION
Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State U niversity
By
JAMES EDWARD COLEMAN, B .S ., M.S.
The Ohio State U niversity 1959
Approved by
Adviser Department of Chemistry ACKNOWLEDGMENT
The author wishes to acknowledge the guidance, suggestions and criticisms of his adviser, Professor
Frank Verhoek, rendered during the course of this investigation.
I also wish to thank Robert C. Petry for the use of his infrared and mass spectra of trimethylboroxin, dimethoxymethylborane and dimethylborylmethylperoxide which were very u sefu l in th is in v e stig a tio n .
The author gratefully acknowledges the monetary assistance afforded by the University Grant-in-Aids
and by the DuPont Research Grant-in-Aid.
- i i - CONTENTS Section Page
I. INTRODUCTION...... 1
II. HISTORY...... 3
k. Oxidation of T rialkylboranes ...... 3
C. Oxplosion Limits ...... 7
C. Oxidation Mechanisms ...... 9
I II. GELS HAL APPARATUS AMD TECHNIQUES...... 11
A. The Vacuum System...... 11
E. Infrared Spectra ...... 16
C. Mass S pectra...... 17
D. Gas Phase Chromatography...... 18
E. Reference Compounds...... 19
1. Hydrogen, Methane and Carbon Monoxide ...... 19
2. Ethane, Carbon Dioxide, Ethyl ene and Acetylene ...... 2 0
3. Trimethylbor oxin ...... 2 0
4. Methoxydimethylborane, Dimethyl- boronous Acid and Dimethylboronous Anhydrid e ...... 21
a. Iodometric test solution..... 21
b. Reaction of trimethylborane and iodometric test so lu tio n ...... 23
c. Reaction of trimethylborane with acetic acid-isopropanol so lu tio n ...... 24
d. Reaction of trimethylborane with glacial acetic acid 24
e. Preparation of methoxydi methylborane 2 5
- i i i - Contents (continued)
Section Page
f. Preparation of dimethyl- boronous acid and anhydride., 26
g. Discussion., ...... 31
IV. rLEPtii.ii.TIOi> A..D P ilLIFICA TI OP1 OF TxvI — METHYLBGL h0E ...... 34
Lq Preparation of Trimethylborane ...... 34
3. Tr ime thylb or ane-Ammonia id duct ...... 36
C. Regeneration from the ammonia adduc t ...... 36
D. P u rity ...... 39
V. HiVESTIGaTIOM OF THE EXPLOSION LIMIT 40
A. Preliminary Explosion Limits ...... 40
1. apparatus ...... 40
2 . Procedure ...... 42
B. Explosion Limits ...... 44
1. Apparatus...... 44
a. Reaction system ...... 4-4
b. Temperature control ...... 49
c. Temperature measurement ...... 51
2. Procedure ...... 52
C . P.e s ult s ...... 55
1. Nature of the Explosion...... 5 5
2. Relationship of the Partial Pressures of Trimethylborane and Oxygen at the Explosion Li mi t ...... 56
- i v - Contents (continued)
Section Page
3. ^ i f e c t of ourPace. - -»..•••.«••••. 04
a. Change in limit with vessel size...... 64
b. Surface conditioning ...... 64
4. Effect of T e m p e ra tu re ...... 66
5. Effect of added l.itrogen ...... 66
6 . Products of .explosions ...... 70
a. Identification of volatile products ...... „. 70
b. Observations concerning the solid coating on the wall.... 85
c. Analysis of the products of four explosions near the lim it at 2 0 . 1 °G...... 86
d. Pressure change for explo sions near the lim it...... 91
VI. INVESTIGATION OF THE KINETICS OF THE REACTION BELOW THE EXPLOSIOii LIMIT...... 98
a. Apparatus...... 93
1. The Reaction System ...... 98
2. The Pressure Transducer ...... 101
3. Temperature Measurement and Control ...... 104
4. The Stopwatch...... 104
B. Procedure...... 105
1. Measurement of I n i t i a l Oxygen Pressure ...... 105
2. Measurement of I n i t i a l Tri methylborane Pressure and Reaction Mixture Pressures ...... 106
- v - Contents (continued)
Section
3. Analysis of the Products ...... 108
C , Treatment of the Data « . . , ...... 110
D „ Results....,...... I l l
1. Products and Stoichiometry of the Reaction...... I l l
a. Analysis of Dimethylboryl- methylperoxide ...... I l l
b. Stoichiom etry ...... 117
2. minor Products ...... 121
a. i» on-c ondensables ...... 121
b. C2 fra c tio n ...... 122
c. Other...... 123
3. Kinetics ...... 12 5
a. Typical curves and in i t i a l r a t e s ...... 125
b. Order of the reaction ......
c. Apparent activation energy... 136
d. Kffect of added gases on the rate of the re a ctio n 137
e. Effect of the product on the rate of the re a c tio n ...... 138
f. E ffect of surface on the rate of the re a c tio n ...... 140
g. In terp retatio n of individual experiments ...... 14.1
h. Comparison of i n i t i a l rates with rate expression...... 151
- v i - Contents (continued)
Section Page
VII. DISCUSSION...... 152
a. Mechanism of the Reaction Below tlie explosion xmx t « 1 5 *-
B. Mechanism of the Reaction at the Explosion Limit ...... 162
C. Suggestions for Future viork ...... 182
VIII. SUMMARY...... 186 aFPE EDIX...... „...... 189 a U T 0 BI Cu. h a F H Y...... 283
B IB LI GGR a PHY ...... 284
- v i i - LIST OF TEXT TABLES Table Page
1. Vapor Pressure of Methoxydimethylborane ...... 26
2. Vapor Pressure of Dimethylboronous acid...... 28
3. Values of "Constants" in Explosion Limit Expre s sion ...... 62
4. Interpretation of Mass Spectra of Explosion Products ...... 72
5. Mass Spectra of Explosion Products...... 76
6 . Summary of Interpretation of Mass Spectra 7?
7. Interpretation of Infrared Spectra of Product Fractions from Explosions ...... 84
8 . Analytical Data of Explosion Products ...... 87
9. Total Pressure Decrease and Peroxide Yield at 19.9°C...... 112
10. Total Pressure Decrease and Peroxide Yield at -20.1°C ...... 114
11. Stoichiometry of the reaction Belov; the Limit at 19.9°C ...... 119
12. Stoichiometry of the reaction Below the Limit at -20.1°C...... „...... 120
13. 'Relative Pressure Decrease of Reaction at -20.1OC...... 121 o 14. Initial Rates for Reaction at 19.9 C ...... 129
15. Initial Rates for Reaction at -20.1°C ...... 130
16. Apparent Activation Energy ...... 13 7
17. I n it ia l Rates of Reaction with Added Gas ......
18. -Initial Rates for Reactions in the Presence of Products ...... I 39
19. Reference Table for Figures 37,38,39 and 40... 146
20. Data for Testing Equation XXI...... 170
- v i i i -
t LIST OF TEXT FIGURES Figure Rage
1. Explosion Limit Examples ...... 7
2. Schematic Diagram of Condensation Train and Storage Unit . . 12
3. Vapor Pressure of Dimethylboronous Acid ...... 29
4. Schematic Diagram of Regeneration System ...... 37
5. Schematic Diagram of Apparatus for Prelimin ary Explosion Limit Experiments ...... 4-1
6. Schematic Diagram of the Explosion Limit Apparatus...... 4-5
7. Cross Sections of Stopcock and Phototube Mountings ...... 47
S. Diagram of Temperature Control System ...... 48
9. Explosion Limit of Trimethylborane and Oxygen in an 8 cm. Diameter Bulb at 25°C ...... 57
10. Explosion Limit of Trimethylborane and Oxygen in an 8 cm. Diameter Bulb at 20.1°C. .. 53
11. Explosion Limit of Trimethylborane and Oxygen in an 8 cm. Diameter Bulb a t 0°G ...... 59
12. Explosion Limit of Trimethylborane and Oxygen in an 3 cm. Diameter Bulb at -20.4°C. .. 60
13. Explosion Limit of Trimethylborane and Oxygen in an 8 cm. Diameter Bulb at -30°G. .... 61
14* V ariation of Total Pressure with Mole- fraction of Oxygen for Explosion Limits in 8 cm. Diameter Bulb at -20.4 and 20.1°C ...... 63
15. Explosion Limit of Trimethylborane andQ Oxygen in a 4.5 cm. Diameter Bulb at 0 C ...... 65
16. Effect of Temperature on the Explosion Limits in an 3 cm. Diameter Bulb ...... 67
17. Explosion Limit of Trimethylborane and Oxygen in an 8 cm. Diameter Bulb at 0°C. Using Air as a Source of Oxygen ...... 68
- i x - List of Text Figures (continued)
Figure Page
18. Explosion Limit of Trimethylb-orane and Oxygen-ditrogen Mixture in an 8 cm. Diameter Bulb at -20.4°C ...... 69
19. Infrared Spectrum of Fraction C of EL 168... 80
20. Infrared Spectrum of Fraction D of KL 168... 81
21. Infrared Spectrum of Fraction E'of EL 168,. 82
22. Infrared Spectrum of Fraction D Qf EL 169 and EL 1 7 2 '...... '83
23. Product D istribution as a Function of Mole- fraction of Oxygen for Explosion near the Limit at 20.1°C...... 88
24.. Relative Mass Balance Obtained from Lon- condensable and C 2 F ractio n s ...... 90
25. Pressure Change for Explosion near the Limit at -20.4°C, in an 8 cm. Diameter Bulb...... 92
26. Pressure Change for Explosion near the Limit at 20.1°C. in an 8 cm. Diameter Bulb ...... 93
27. Relative Pressure Change for Explosions near the Limit at -2 0.4.°C. in a u 8 cm. Diameter Bulb...... 95
28. Relative Pressure Change for Explosions near the Limit at 20.1°C. in an 8 cm. Diameter Bulb...... 96
29. Schematic Diagram of Reaction System for Kinetic Experiments ...... 99
30. Transducer Mounting ...... 100
31.. Wiring Diagram for Pressure Transducer C irc u it ...... 103
32. Typical -&n-Time Curve...... 126 IT 33. Typdcal Rate-Trimethylborane Curves ...... 128
-x -
t List of Text Figures (continued)
Figure Page
34. Determination of Oxygen Order for Reaction at 19.9°C. in a Spherical Reactor ...... 131
35. Determination of Trimethylborane Order for Reaction at 19.9°C. in a Spherical Reactor 133
36. Determination of Overall Order fo r 1:1 Mixture of Oxygen nd Trimethylborane at 19.9°C. in a Spherical Reactor ...... 134
37. Test of the Retarding Effect of the Reactants.. 142
38. Test of the P;etarding Effect of the Reactants.. 143
39. Test of the Retarding Effect of the Reactants.. 144
40. Test of the lietarding Effect of the Reactants.. 145
41. Activation Energy P lo t ...... 166
42. Test of Equation XXI...... 171 APPENDIXES Page
APPENDIX A Infrared Spectra of Reference Compounds ...... 189
APPENDIX B Mass Spectra of Reference Compounds ...... 200
APPENDIX C Explosion Limit Data ...... 204
APPENDIX D Gas Phase Chromatographic Analysis ...... 215
APPENDIX E Kinetic Experiment Data ...... 222
APPENDIX F Special Experiments with Kinetic Experiment Products 260
APPENDIX G Estimation of Flame Temperatures 275
- x i i - LIST OF APPENDIX TABLES
Table ” PaSe
B-l Mass Spectra of Reference Compounds, ...... 201
C_1 Preliminary Explosion Limits at 0°C. in an 8 cm. Diameter Bulb...... 205
C-2 Preliminary Explosion Limits at 0°C. in a 4.5 cm. Diameter Bulb...... 2 06
C-3 Preliminary Explosion Limits at 0°C. in a 4.5 cm. Diameter Bulb using Air as a Source of Oxygen ...... 2 07 o C-4 Preliminary Explosion Limits at -30 C. in an 8 cm. Diameter Bulb ...... 208
C-5 Preliminary Explosion Limits at 25°C. in an 8 cm. Diameter Bulb...... 2 09
C- 6 Explosion Limits at -20.4OC. in an 8 cm. Diameter Bulb...... 210
C-7 Explosion Limits at -20.4°C. in an 8 cm. Diameter Bulb Using a 76.6 per cent oxygen in Nitrogen Mixture as a Source of Oxygen 213
C- 8 Explosion Limits at 20.1°C, in an 8 cm. Diameter Bulb ...... 214
D-l Retention Times for Gas Phase Chromatography Peaks...... 216
D-2 C alibration Factors for Gas Phase Chromato graphy Peaks...... 218
D-3 Gas Phase Chromatographic Analysis of Non-condensable Fractions ...... 219
D—4 Gas Phase Chromatographic Analysis of G2 Fractions...... 220
D-5 Summary of Analysis of Non-condensable F ractio n s ...... 221
D- 6 Summary of Analysis of C 2 F ractio n s ...... 221
E -l Data for Experiments K-l and K-2 ...... 227
E-2 Data for Experiments K-3 and K-4 ...... 228
- x i i i - L ist of Appendix Tables (continued)
Table Page
E-3 Data for Experiments K-5 and K-6 ...... 229
E-4 Data for Experiments K-7 and K-8 ...... 230
E-5 Data for Experiments K-8-P and K-9 ...... 231
E-6 Data for Experiments K-10 and K-ll...... 232
E-7 Data for Experiments K-12 and K-13 ...... 233
E-8 Data for Experiments K-14 and K-15 ...... 234
E-9 Data for Experiments K-16 and K-17 ...... 235
E-10 Data for Experiments K-17-P and K-18 ...... 236
E-ll Data for Experiments K-18-P and K-19 ...... 237
E-12 Data for Experiments K-20 and K-21 ...... 238
E-13 Data for Experiments K-22 and K-23 ...... 24-0
E-14- Data for Experiments K-24- and K-25 ...... 24-1
E-15 Data for Experiments K-26 and K-27...... 242
E-16 Data for Experiments K-28 and K-29 ...... 243
E-17 Data for Experiments K-30 and K-30-P ...... 244
E-18 Data for Experiments K-31 and K-32 ...... 246
E-19 Bata for Experiments K-33 and K-34 ...... 248
E-20 Data for Experiments K-35 and K- 3 6 ...... 250
E-21 Data for Experiments K-37 and K- 3 8 ...... 251
B-22 Data for Experiments K-39 and K-40...... 254
E-23 Data for Experiments K -41 and K-42 ...... 255
E-2 4 Data for Experiments K-43 and K-44 ...... 256
E-25 Data for Experiments K -45 and K- 4 6 ...... 258
E-26 Data for Experiments K -4 7 and K- 4 8 ...... 259
- « iv - List of Appendix Tables (continued)
Table Page
F-l Mass Spectrum of K--34- Condensables ...... 267
F-2 Mass Spectrum of K-35 Residue with Possible Interpretation ...... 271
F-3 Mass Spectrum of K-39 Fraction with Possible Interpretation ...... 274-
G-l Thermodynamic Data for Maximum Flame Temperature ...... 277
G-2 Thermodynamic Data for Minimum Flame Temperature...... 279
G-3 Thermodynamic Data for Probable Flame Temperature...... 2S1
-x v - LIST OF APPENDIX FIGURES
Figure Page
A-l C alibration Curve for Perkin-Elraer Model 21 Spectrophotometer Serial No. 178 ...... 190
A-2 Infrared Spectrum of Trimethylborane ...... 191
A-3 Infrared Spectrum of Methoxydimethylborane... 192
A-4 Infrared Spectrum of Dimethoxymethylborane... 193
A-5 Infrared Spectrum of Dimethylborylmethyl- por oxid e ...... 194
A-6 Infrared Spectrum of Hydroxydimethylborane... 195
A-7 Infrared Spectrum of a Mixture of Hydroxy dimethylborane andOxybis(dimethylborane).... 196
A-8 Infrared Spectrum of Trimethylbor oxin ...... 197
A-9 Infrared Spectrum of Neopentane ...... 198
A-10 Infrared Spectrum of Pyridine...... 199
E-l Transducer Calibration No. 1, Temperature 19. 9°C ...... 226
E-2 Transducer Calibration No, 2, Temperature -20.1°C ...... 239
E-3 Transducer Calibration No. 3, Temperature 1 9 .9°C ...... 245
E-4 Transducer Calibration No. 4, Temperature - 2 0 .1°C...... 247
E-5 Transducer Calibration No. 5, Temperature 1 9 .9°C...... 249
E-6 Transducer Calibration No. 6, Temperature 19.9°C ...... 252 (Scale 10 = 1 v o lt) E-7 Transducer Calibration No. 7, Temperature 19.9°C ...... 253
E-8 Transducer Calibration No. 8, Temperature - 2 0 .lo c ...... 257
- x v i- List of Appendix Figures (continued)
Figure Page
F-l Infrared Spectrum of Neopentane Fraction of K-31 ...... 262
F-2 Infrared Spectrum of Vapor over the Pyridine Abduct of the Products of K-31 ...... 263
F-3 Infrared Spectrum of Vapor over the Pyridine Adduct of the Products of K-34 ...... 269
- x v i i - I. INTRODUCTION
Trialkylborsnes have been known to react spontane ously with oxygen since Frankland's observations (1,2,3) on trimethyl- and triethylborane which were made almost a century ago. In view of the considerable interest in boron chemistry in recent years, it is surprising that there have been so few in v e stig a tio n s of the k in etic s of the oxidation of these compounds.
Bamford and Newitt (4-) studied the oxidation of trimethylborane and concluded that the reaction below the explosion lim it proceeds by a chain mechanism which begins and ends on the walls and yields a single product with the general formula BMe^O^. At low pressures and o 2$ C. the rate was given by the expression
rate
However, at moderate pressures (5 mm. of BMe^ and 2,5 to
12 mm. of 0^) the order with respect to oxygen appeared to be about 1.6. At still higher pressures ignition was found to occur. In view of the speed of the reaction, its chain nature and the fact that it changes from a single product to an explosion over a small range of pressure, it was of interest to extend the study of this reaction.
In the investigation reported here, a study has been made of the explosion limits and their relationship to the pressures of the reactants and the temperature. Included - 2 - in these studies are the effects of vessel size and added inert gas on the explosion limits.
The kinetics of the reaction at pressures below the explosion limit were restudied and investigations made for effects of temperature, added gases and change in the surface to volume ratio of the vessel. The kinetics dur ing the course of a single experiment were also investi gated. II. HISTORY
A. The Oxidation of Trialkylboranes
The first report of the oxidation of a trialkyl- borane was made by Frankland (1,2,3) in 1859. He ob served that trimethyl- and triethylborane exhibit two distinct kinds of spontaneous combustion. When issuing very slowly into the air from a glass tube, "They burn with a lambent blue flame...the temperature of which is so low that a finger may be held in it." At more rapid rates of flow they burn with a hot green flame. Frank land also reported that controlled oxidation of triethyl- borane yielded diethoxyethylborane which he characterized by hydroxysis giving dihydroxyethylborane and ethanol.
Later Meewein and Sftnke (5) reported that the con trolled oxidation of triethylborane yielded ethoxydiethylborane, , die thoxyethylborane and triethosybora ne .
Krause and co-workers (6,7,8,9,10) prepared a number of trialkyl- and triarylborane3 (R in R^B = n-propyl, sec-butyl, tert-butyl, isoamyl, cyclohexyl, phenyl, benzyl, p-tolyl, p-xylyl, p-anisyl and a-naphthyl) and reported all were readily oxidized by air with the exception of a-naphthyl which was attacked very slowly. (More recently
Brown and Sugishi (11) reported that the tri-a-naphthyl- borane showed no oxidation a fter a y ea r’ s contact with air).
Also the hydrolysis of the reaction mixtures from the
-3 - > controlled oxidations of triisoamyl-, triisobutyl- and tri-n-propylborane yielded the 'corresponding dihydroxy- alkylboranes (6). The initial products were believed to be the corresponding alkylboron oxides, RBO.
Johnson and Van Campen (12) observed that 0,67 mmoles of tri-n-butylborane reacted with dry air causing a reduction of the air volume corresponding to the con sumption of 0,65 mmoles of oxygen. Oxidation of a larger sample by allowing it to stand six months in a loosely stoppered test tube yielded a single product which on hydrolysis produced dihydroxy-n-butylborane and n-butyl alcohol. When the oxidation was performed in moist air only half as much oxygen was consumed and the reaction product yielded hydroxydi-n-butylborane and n-butyl alcohol on hydrolysis. The authors concluded that the oxidation was a step-vrise process in which the oxidation of n-butoxydibutylborane to di-n-butoxy-n-butylborane is inhibited by water,
Bamford and Newitt ( 4 ) made the first kinetic study of the oxidation of a trialkylborane. They investigated the oxidation of both trimethyl- and tri-n-propylborane, but found the latter reaction too fast to measure with their apparatus. In most of their experiments trimethyl borane was admitted at a rate of about 0,1 mm/min. to the reaction vessel (8 cm. dia. bulb) containing oxygen at a known pressure at 25°C. while pressure measurements were -5 - made at suitable intervals. k typical experiment had an induction period of 2 to 3 minutes, produced a pressure decrease corresponding to the formation of a compound of the formula BMe^C^, and could be inhibited by the action of volatile compound(s) formed by a surface reaction be tween water and trifluoroborane. The inhibition appeared to be homogeneous. Rates corresponding to the time when the admission of trimethylborane was stopped were obtained and found to be in agreement with the expression
rate = k
A waxed v essel gave b etter agreement than unwaxed v e s s e ls .
Moderate pressures of nitrogen had no measurable effect on the rate of reaction but large pressures of nitrogen or oxygen caused deviation from the rate expression mentioned above. This was attributed to a diffusion effect.
Fox- experiments at higher pressures,- oxygen was very quickly introduced into the reaction vessel (6 cm. diam. bulb) containing a known pressure of trimethylborane.
Maximum rates obtained in these experiments consistent with a 1.6 order with respect to oxygenj however, the authors believed that the true order was 2 and that tur bulence in the gas was responsible for the apparent de crease in order. At higher pressures ignition occurs and an explosion limit curve was obtained for reaction in a
6 cm. diam. bulb at 25°G. There were no appreciable -6- induction periods for the explosions and ignition could be suppressed by mixtures of trifluoroborane and water.
The authors concluded that reaction proceeded by a chain process beginning and ending on the wall and that little branching occurred except near the explosion limit.
In an investigation on the explosion limits of 5 volume per cent mixtures of triethylborane in oxygen (13), it was reported that below the explosion lim it, ’’there was no pressure change or detectable deposit in 1,000 seconds."
Recently Petry and Verhoek (14-) prepared the oxidation product of trimethylborane in a flow system and identified the product as dimethylborylraethylperoxide. Petry (15) investigated the thermal decomposition of the peroxide in gas and liquid phases. The major product of the decomposit ion was found to be dimethoxymethylboranej however, numerous other products in much smaller amounts were identified among which were methoxydimethylborrue, trimethoxyborane and trimethylboroxine.
Abraham and Davies (16) also reported the formation of organoboron peroxides in the autooxidation of tributyl- boranes in dilute cyclohexane solution. From the oxida tion of partially isomerized tri-tert-butylborane they isolated a product which they characterized as W (°°V 9)2. -7 - .
B. Explosion Limits
A complete review of explosion limits is beyond the
scope of this report. Therefore, only a brief mention
of some of the various relationships which have been ob
served w ill be made. In Figure 1 are sev era l examples of
explosion limit phenomena; I, II and III give pressure-
temperature relationships which are usually obtained for
a fixed fuel to oxygen ratio. I and II are characteris
tic of the hydrogen-oxygen reaction (17), and hydrocarbon-
oxygen reactions (17), respectively. Ill has been
observed for the diborane-oxygen reaction (18,19). In
the other examples are relationships between the pressure
of the fuel and the pressure of the oxygen when experi
ments are performed in a vessel of a given size .at a
specified temperature. The plot given in IV is for the
reaction of hydrogen and oxygen (20). That in V was ob
served for diborane and oxygen (21). VI is typical of the
results observed for the oxidation of pentaborane-9 (22),
dialkyl zinc ( 4 , 2 3 ) and trimethylborane (4)j however, the
curvature of the relationship varies from compound to
compound in addition to variations with temperature, vessel size and condition of the walls. In the case of
dimethyl zinc (23) and pentaborane-9 (22) the limits are
increased for a decrease in vessel size and are decreased for an increase in temperature. (Unlike V these changes cause a displacement of the entire curve.) Fuel pressure Pressure Pressure i. . xlso Lmt xmples. Exam Limit Explosion I. Fig. Non-explosion 4.6cm. dia. bulb xgn pressure Oxygen Explosion Temperature T emperature 1 N Explosion Explosion 5.8cm. bulbdia. I -8- CL a> o> U_ u. 3 u. a. a> a u 3 — j Non-explosion xgn pressure Oxygen xgn pressure Oxygen Explosion Temperature Explosion Explosion flame Cool EZ -9-
The effect of product coating of the walls has been observed to raise the limits in the case of the pentaborane-9 reactionj however, for coated vessels the temperature variation was no longer observed. In the reaction of 5 volume per cent mixture of triethylborane in oxygen, the product of minimum pressure for ignition and bulb diameter was found to be constant (13)j here too a product coating raised the lim its.
C. Oxidation Mechanisms
Little is known of the mechanism of the oxidation
of trialkylboranes. The step-wise oxidation through the monoester R^BOR (12) seems very unlikely in view of the later observations showing the formation of peroxides
(15,16). The chain nature of the reaction has been shown by Bamford and Newitt (4); however, their mechanism was proposed under the belief that the product was the diester
RB(0R)2 rather than peroxide R 2BOOR. The only in te r pretation of their mechanism consistent with the actual
product is that an energy chain is involved rather than a radical chain. In view of the actual product Petry proposed a radical mechanism involving the formation of an alkyl peroxy radical and its subsequent reaction with the trialkylborane by means of a radical displacement.
Because of this lack of information on the mechanism of the oxidation of trialkylboranes, it will be informa tive to mention briefly the mechanisms of oxidation of -10- two-classes of compounds which may be considered as re lated classes; namely, hydrocarbons and boron hydrides.
The contemporary theory of hydrocarbon oxidation is that it proceeds by degenerate chain branching (2 4.). Both aldehydes (25) and peroxides (26,27) have been proposed as intermediates responsible for chain branching. Theo retical considerations of the kinetics of the oxidations have been extensively discussed (17) and elemental r e actions have recently been reviewed (2$,29).
Mechanisms of the oxidation of boron hydrides have been investigated mainly by determination of explosion lim its and conditions affecting them. The most extensive studies have been on diborane (18,19,30) from which it has been concluded th a t near the first explosion limit branching and breaking occur at the wall and near the second limit they occur in the gas phase. Inert gas ef fects indicate that near the second limit branching is bimolecular and chain breaking is trimolecular. The proposed reaction mechanism (18) is p a rtia lly analogous to the hydrogen-oxygen reaction (17) (substituting B2H^ for Hg , BH^ for H* and BHgOH for HO*).
A. first explosion limit has been observed for penta- borane-9 (22,31) and a general mechanism proposed, however, no specific intermediates have been proposed. III. GENERAL APPARATUS AND TECHNIQUES
A. The Vacuum System
Because of the reactivity of trimethylborane with oxygen and the v o l a t i l i t y of the compounds involved, the investigations reported here were performed in a conven-
— *5 m m f i ) tio n a l vacuum apparatus (32). A vacuum of 10 to 10” mm. of mercury was readily produced by a Welch Duoseal forepump and a mercury diffusion pump. The latter was connected through a liquid nitrogen trap to a manifold which served the individual units of the system. Pressure in the manifold was measured with a McLeod gauge. Iso lation of individual components of the system was accomplished by the use of vacuum grade stopcocks which were usually greased with Apiezon greases N or T. In a few applications it was necessary to use Dow Corning
High Vacuum Grease.
In general 10 to 12 mm. o. d. tubing was used throughout the apparatus. The vacuum manifold and the connections to the pumps were constructed of 25 mm. o. d. tubing. The gas storage unit and the condensation train are shown in Figure 2. The gas storage bulbs were con structed from 5 liter flasks and were furnished with mercury—protected stopcocks in order to prevent prolonged contact with stopcock grease. The mercury-protected stopcocks also served as a safety device in that any
-11- To vacuum manifold
Storage bulbs Calibrated volume Hg manometer Stirring motor To ai r To vacuum manifold To vacuum
Hg reservoir
Vp-1 bulb u ^ s Weighing Seal-off tube <-> y / bulb Ky \y v ^ / J U Condensation traps ; Degassing trap Tube opener Transfer tube I Hg manometer S02 vapor pressure thermometer
Fig. 2. Schematic Diagram of Condensation Train and Storage Unit. -1 3 - leakage of air through the stopcocks could be detected
by displacement of the mercury column and the air could be pumped out without coming in contact with the gas
stored. Also attached to the gas storage submanifold was a 1 liter flask connected to a mercury manometer.
After calibration of the volume, this flask was used both for measuring amounts of gas and for storage pur
poses.
The traps of the condensation train were fabricated from 50 cc. flasks. Attached to the condensation train
submanifold was a vapor pressure unit used to identify
the various fractions obtained in the condensation train.
The vapor pressure unit consisted of a mercury manometer with an adjoining vapor pressure bulb, a stirrer and a thermometer. For the temperature region of -10 to -60°C. a sulfur dioxide vapor pressure thermometer was used.
Calibration of the volumes of the vapor pressure unit
(30.6 cc. at zero pressure) and the submanifold
(170.8 cc.) allowed their use for measuring small amounts of gases. Low temperatures for vapor pressure measure ments and vacuum fractionation were produced by slush baths whose approximate temperatures are listed below: - 1 4 -
Slush Bath Temperature
t-A.myl alcohol -12
Carbon tetra ch lo rid e -2 3
Chlorobenzene -4 6
Chloroform —64
Dry Ice-scetone - s o
Ethyl benzene -9 3
Ethyl bromide -1 1 8
Methyl cyclopentane -142
The submanifold of the condensation train was also equipped with S 12/30 outer joints for the attachment of various accessories. Such accessories included seal-off tubes for storage of condensable materials, a tube opener for return of stored materials to the system, transfer tubes for moving samples to other systems (for example, the mass spectrometer), weighing bulbs, etc. Two types
of weighing bulbs were used. The first type consisted of a bulb (various sizes used) with attached stopcock and inner joint. The second type was made from 50 cc. flasks with flattened bottomsj each carried a 10/30 outer joint (corresponding inner part served as a cap) in addi tion to the usual stopcock with ^ 12/30 inner joint. This extra joint was very useful as it made introduction of solvents and solution simple and facilitated the cleaning of the bulb.
When solvents or solutions were introduced into the - 1 5 - system, a degassing trap was usually used for the degassing of the liquid. The following technique was used: the trap and weighing bulb were immersed in the liquid nitro gen and, when co o l, opened to the vacuum pumps. After a sufficient vacuum was obtained, the liquid nitrogen bath was removed from the weighing bulb and the weighing bulb allowed to warm slowly until the major portion of the li quid had distilled into the degassing trap. The material collected in the trap was condensed back into the weighing bulb and the freezing and pumping process repeated. If the weighing bulb was allowed to reach room temperature between cycles, three cycles were sufficient for a degassing of the order of 10 ^ mm. Solutions introduced in this manner were utilized in the weighing bulb.
Additions and modifications to the vacuum system for specific investigations will be mentioned in the appropri ate sections.
The Pyrex glassware used throughout the system was cleaned in concentrated nitric acid followed by several rinsings with distilled water. In cleaning used glassware
Apiezon greases and waxes were removed with chloroform and dried before using nitric acid. Removal of Dow Corning
High Vacuum Grease was accomplished by rinsing with car bon tetrachloride or benzene followed by treatment with potassium dichromate-sulfuric acid cleaning solution.
Volumes of various u n its were calib rated by one of -1 6 - two methods. The volumes of items which were readily removed from the system were measured by determining the weight of water contained at a given temperature. These volumes are referred to as standard volumes. Other vol umes were measured by expanding or condensing a gas of known volume and pressure into the unknown volume, meas uring the new pressure after temperature equilibration, and applying Boyle's Law. These volumes are referred to as calibrated volumes,
B. Infrared Spectra
Infrared spectra of various gaseous samples were obtained on a Perkin-Elmer Model 21 Infrared Spectrometer with a sodium chloride prism. All spectra were run with the controls at the following settings: resolution 920 , response 1, gain 6, speed 5, and suppression 2, Two different gas cells were used in the course of this work,
A 9,5 cm. stainless steel absorption cell with sodium ch lorid e windows was used whenever a sample of s u ffic ie n t size was a v a ila b le. For those samples which were quite small, a cell which had a much smaller volume was used.
This cell, constructed of Pyrex tubing and sodium chloride windows, did not utilize the full sample beam; and because of this, a wire screen was placed in the reference beam to obtain higher transmittance values for regions in which the sample did not absorb. This was done with some loss in resolution. -1 7 -
Photographs of reference spectra along with a cali bration curve are given in Appendix A. Wave length corrections may be obtained by use of the calibration curve and the water vapor absorption obtained from the reference beam.
The author is indebted to Charles R. Weisend for his aid in the operation of the spectrometer.
C. Mass Spectra
The mass spectra of various samples were obtained with a General Electric Analytical Mass Spectrometer operated at a 75 volt ionizing potential. This instru ment gives peak height as a function of magnet in te n sity .
Valiies of m/e 1 1 unit were obtained from a calibration curve. Determination of the spectrum of a sample after the admission of air provides an internal calibration at the following values of m/e: 14(nitrogen), l 6 (oxygen),
28 (nitrogen), 32(oxygen), 4-0(argon) and 44(earbon dioxide).
The values of the relative intensities-^- of reference
Relative intensities are calculated by the equation: j ______Peak Height X 100 ______Peak height of stro n g est peak compounds greater than 0.5 are lis t e d in Appendix B.
The author is indebted to John W. Kraus, William C.
Sleppy and Charles R. Weisend for their operation of the mass spectrometer. -1 3 -
D. Ga3 Phase Chromatography
Gas phase chromatography was used for checking the
purity of the oxygen used, for measuring the composition
of oxygen-nitrogen mixtures, and for the identification
and analysis of the more volatile reaction products. The
author is indebted to George H. Hembree (33) and George
Kyryacos ( 34) for the use of their gas phase chromato
graphic apparatus, descriptions of which may be found in
their respective Ph.D. dissertations, and also to Joseph
k. Lovinger for use of his apparatus (unpublished).
Analysis of gaseous products obtained with gas phase
chromatography were performed in the following manner:
the amount of the p a rticu la r gas fr a c tio n was determined
in a gas burette by measuring pressure, temperature and
volume. A portion of the sample was then introduced into
a loop of known size at a measured pressure and tempera
ture; this loop was then introduced into the helium stream
of the proper chromatographic column and peak heights for the various gases present were measured at their respective retention times. Calibration factors were obtained from the peak heights of standard known mixtures and composit ion of a given sample readily calculated.
The results of the gas phase chromatographic analyses are given in Appendix D. - 1 9 -
El. Reference Compounds
1. Hvdroeen. Methane and Carbon Monoxida
A standard mixture of 33.7# hydrogen, 33.3# methane, and 33. 0# carbon monoxide was made for calibration of the gas phase chromatography column for non-condensables, The gases used were obtained from various tanks in the follow ing way: a gas sampling tube, consisting of a glass tube with stopcocks and attached joints at each end, was evacuated. A needle valve and Tygon tubing were attached to the gas tank and were flushed with the gas. The sampling tube was attached to the tubing and the first stopcock opened. When the pressure exerted on the Tygon tubing indicated that the pressure was slightly above atmos pheric, the second stopcock was opened and the sampling tube was flushed with the gas being sampled. Finally the stopcocks on the sampling tube were closed and the Tygon tubing detached. The sampling tube was attached to the vacuum system and a sufficient sample of the gas pumped into a gas burette by the Toepler pump. After measuring the sample it was moved into another gas sampling tube where it was kept until used. In this manner 8,59 mmoles of Matheson C.P. carbon monoxide, 8.66 mmoles of P h illip s
Research Grade methane, and 8.78 mmoles Airco hydrogen were measured and transferred into the same sampling tube. -2 0 -
2, Ethane T Carbon D ioxid e. Ethylene a nd Acetylene
A standard mixture of 10,9$ ethane, 34-.0% carbon dioxide, 20.7$ ethylene and 34*4% acetylen e was made for the calibration of the gas phase chromatography column used for analysis of these gases. (Note: the fraction that contained these gases was referred to as the C/j fr a c tio n .) The method of obtaining the gas samples was the same as that mentioned above; however, after introduction into the vacuum system each of these gases was distilled in a vacuum from a trap at -142°C. and collected at -196°C. A portion of each gas sample was measured out by obtaining P-V-T data for the sample by using the combined volume (calibrated) of the vapor pressure unit and the submanifold of the condensation train (see Fig. 2). In this manner 2.61 mmoles of Phillips
Research Grade ethane, 8.15 mmoles of carbon dioxide, 4.97 mmoles of Phillips Research Grade e thylene and 8.27 mmoles of commercial acetylene were purified and measured. The gases were condensed in a small tube adjoining a gas sampl ing tube; the tube was opened and the gases rapidly vapor ized and expanded into the sampling tube. After allowing
35 minutes for mixing equilibrium the gas sampling tube was isolated. The gases were kept in this tube until used.
3• Trime thvlboroxin
The infrared spectrum and the mass spectrum of tri- methylboroxin were obtained from Petry (15). -21-
4. Methoxvdimethvlborane. Dlmethvlboronous Acid and 2 Dimethylboronous Anhydride
o The American Chemical Society Advisory Committee on
the Nomenclature of Organic Boron Compounds has suggested
that these two compounds be named hydroxydimethylborane and oxybisdimethylborane, respectively. The older names
are used in this section for convenience and to emphasize
their relationship.
Since the method of preparation of these m aterials was based on the results of an investigation of the presence of a non-condensable gas over a sodium iodide- isopropanol solution containing glacial acetic acid after it has been used to destroy diraethylborylmethylperoxide in the presence of trime thylbor ane, it seems appropriate to report the entire investigation.
a) Iodometric test solution. The product of the non-explosive oxidation of trimethylborane had been identified as being dimethylborylmethylperoxide ( 14) and
Petry ( 15) has d eveloped an iodom etric method of a n a ly sis of th is compound. This same method was used by the author and the test solution was also used to destroy the peroxide obtained from non-explosion experiments in the investigation of the explosion limits. The test so lu tio n was made in the follow ing manner: a so lu tio n of -22-
Baker C.P. sodium iodide in isopropanol (Union Carbide
99 $ which had previously been distilled through a three- foot, glass helix-packed column) was prepared by swirling
100 cc. of isopropanol with an excess of sodium iodide in an Erlenmeyer flask. The solution was decanted and the liquid portion added to an equal amount of isopropanol.
The resulting solution was then introduced into a 250 cc.
Erlenmeyer flask, the neck of which had been drawn down to accomodate a serum cap. Linde H.P. dry nitrogen was then bubbled through the solution for approximately ten minutes in order to displace dissolved oxygen and finally the flask was stoppered with a serum cap. Similarly glacial acetic acid (Du Pont Reagent) was deoxygenated and stored under nitrogen in a 50 cc. Erlenmeyer flask equipped with serum cap.
The final test solution was prepared by successively introducing with the aid of a syringe 15 cc. of the al coholic sodium iodide solution and 2 cc. of the glacial acetic acid into a 50 cc, weighing bulb (by way of the side arm) which had previously been flushed with nitrogen.
The solution was then degassed in the manner previously described (see Section III-A).
S olu tion s made by the above method could be prepared from the same master solution over a period of several weeks and still yield a colorless test solution. -23-
b) Reaction of triraethylborane and iodometric test
solution. During the explosion limit experiments it was
customary to destroy the peroxide from several non-explos
ive experiments by adding the condensable fractions to the
same test solution. When this was done after experiments
in which there was initially present more trimethylborane
than oxygen, a non-condensable gas was formed and the r e
sulting solution was lighter in color. In an experiment
in which trimethylborane alone was added to a solution
containing iodine from previous reaction with peroxide,
appreciable quantities of gas were produced and the solu
tion was completely decolorized.
The phenomenon was further in v estig a ted in the
following experiment. To 20 cc. of a degassed isopropanol
solution containing 20.94 mmoles of glacial acetic acid
and 0.168 mmoles of iodine (no iodide p resen t), 0.150
mmoles of trimethylborane was sdded. Occasional freezing
of the solution and pumping of the non-condensable gas over
a three day period yield ed 0.102 mmole of methane ( 0.666
mmole of methane per mmole of trim ethylborane i n i t i a l l y
present) identified by gas phase chromatography. Titrat
ion of the solution with sodium thiosulfate indicated that
only 0.100 mmole of iodine was present ( 0.453 mmole of
iodine lost per mmole of trimethylborane initially present).
Possibly a portion of the iodine loss could be attributed -24- to reaction with mercury in the system.
c) Reaction of trimethylborane with acetic acid-
isopropanol solution. From the above experiment it
was apparent that trimethylborane was reacting with the
iodine and something else in the solution. Therefore
the following experiment was made to characterize the
latter reaction. To a degassed solution of 17.45 mmoles
of glacial acetic acid in 10 cc. of isopropanol, 0.158
mmoles of trimethylborane was added. The solution was
heated to 50°C. for approximately 40 minutes then frozen
with liq u id nitrogen and 0.135 mmoles of methane pumped
off and c o lle c te d . Occasional freezin g and pumping over
several days raised the total methane yield to 0.155
mmole ( 0.981 mmoles of methane per mmole of trimethyl
borane initially present). Thus the reaction gives one
mole of methane for each mole of trim ethlyborane and the
reaction is quantitative within the limits of experimental
error.
In an experiment in which 0.164 mmoles of trimethyl borane in 10 cc. of isopropanol containing no iodine nor
acetic acid, only a negligible amount of gas was formed.
d) Reaction of trimethylborane with glacial acetic
acid. To 1.745 mmoles of degassed acetic acid, 0.181 mmoles of trimethylborane was addedj the mixture was then heated to 50°C. for approximately thirty minutes, after which 0.206 mmoles of methane was collected. Then 0.6 cc. -2 5 - of degassed methanol was added to the reaction mixture.
After allowing mixture to stand for several hours at room temperature, it was again frozen and 0.018 mmoles of methane collected. Total methane collected was 0.24.4- mmoles ( 1.24 mmoles of methane per mmole of trimethyl borane i n i t i a l l y p resen t). The methanol was added in hope of making methoxydimethylboranej however, i t s isolation from the reaction mixture was not accomplished.
e) Preparation of methoxydimethylborane. In a weighing bulb containing 0.349 mmole of degassed glacial a cetic acid and 0.850 mmole of degassed Coleman and B ell
Reagent Grade methanol, 0.830 mmole of trimethylborane was condensed and allowed to stand at room temperature. Over a period of three days the materials were occasionally frozen and the methane (identified by gas phase chromato graphy) was pumped into a gas burette. A total of 0.826 mmole of methane was obtained ( 0.995 mmole of methane per mmole of trimethylborane initially present).
The reaction mixture was fra ctio n a ted in vacuum using traps at -80, -118 and -196°C. Methoxydimethyl borane (0.796 mmole) was thus isolated in the -118° trap
(0.960 mmole methoxydimethylborane per mmole trimethyl borane initially present). The product was identified by its molecular weight (found 73.8, theoretical 71.9) and by comparison of its vapor pressure with that calculated from the equation -2 6 -
log pM = 7.935 - ■ reported by Burg and Wagner (35) - see Table 1.
TABLE 1
VAPOR PRESSURE OF METHOXYDIMETHYLBORANE
Temperature, °C. -7 9 .0 - 63.0 -4-8.5 - 30.0 0.0 Vapor Pressure, obs. (mm.) 2.0 6.3 19.9 66.2 302.9 Vapor Pressure, c a lc , (mm.) 1.8 7.0 20.0 64.O 301.2
The chemical equation for the preparation of methoxydi methylborane is
(CH3)3B + CH^OH - A---> CH^ + (CH^BOMe.
The infrared and mass spectra are listed in Appendix
A and Appendix B, respectively.
f ) Preparation of dimethylboronous acid and an hydride. In a 500 cc. bulb were placed 9.974. mmoles of d is t il le d water, 0.34-9 mmole of g la c ia l a c e tic acid and
10.897 mmoles of trimethylborane. Reaction occurred at room temperature and over a period of eleven days 10.516 mmoles of methane were removed. Repeated fractionation of condensable products yielded 0.173 mmoles of material which passed through a trap at -118°G. This was believed to be unreacted trimethylborane. The remaining material was fractionated repeatedly through traps at - 4.6°, - 64.0,
-80° and -196°C. The -4.6° trap yielded only a small amount of m aterial which was discarded. R efraction ation -2 7 - of the material collected in the - 640 trap y ield ed two samples of dimethylboronous acid. (Total yield was
0.2536 g. or 40$ of the initial trimethylborane.) By measurement of PVT data and weight of sample the molecu lar weight of each sample was determined; sample 1
(2.73 mmole) gave 57.8 and sample 2 ( I .64 mmole) gave
58.4 (calculated value is 57.88). The infrared spectrum
(see Appendix A) has a strong band at approximately 2.8 microns, indicating the presence of a hydroxyl group.
Further proof that the material is dimethylboronous acid comes from the fact that the methanolysis of sample 2 was carried out by Petry (15) and yielded methoxydi methylborane quantitatively within the limits of experi mental error. The mass spectrum (Appendix B) obtained from sample 1 is consistent with that which might be ex pected, although the two highest peaks may indicate the presence of a small amount of the anhydride. The vapor pressure of sample 1 was determined for the range -5 to o 25 C. and is reported in Table 2. The logarithmic plot of the vapor pressure as a function of the reciprocal of the absolute temperature (Fig. 3) results in a straight line given by the equation:
log pmm = 9‘697 - 2218/T. From the equation the molar heat of vaporization is cal culated to be 10.2 kcal. mole ^ and the extrapolated boil ing point is 52.3°C. -2 8 -
TABLE 2
VAPOR PRESSURE OF DIMETHYLBORONOUS ACID
Temperature a Vapor Pressure l/T x 10^ °C. (mm.)
22.0 148.5 3.389 20.5 136.8 3.406 19.2 127.4 3.421 17.5 115.3 3.441 16.2 107.0 3.457 U . 7 97.9 3.475 12.8 87.2 3.498 10.8 77.2 3.522 8.5 66.8 3.551 6. 5 58.0 3.577 3.2 46.7 3.619 -0 .3 36.8 3 • 666 -4 .5 27.7 3.723 -4 .6 26.6 3.724 4.1 48.8 3.608 9.9 70.6 3.534 13.3 87.8 3.492 16.2 105.1 3.457 19.4 127.8 3.419 22.1 148.8 3.388 23.2 159.2 3.375
Values are listed in the order of measurement. 2 0 0
100
80
6 0
4 0
20
10 3.3 3.4 3.5 3.6 3.7 3.8
- f x I 0 3
Figure 3. Vapor Pressure of Dimethylboronous Acid. -3 0 -
Ulmschneider and Goubeau ( 36) have reported the
preparation of the dimethylboronous acid from the reac
tion of trimethylborane and water at 200°C. They
reported a heat of vaporization of 9.76 kcal/mole, a
calculated boiling point of 56° and the following vapor
p ressu res:
Temp., °C. 0.4 4.6 10.5 14.5 18.0 22.0 25.3 23.6 35.0 Pressure mm.of Hg. 36 49 70 91 110 140 168 201 281
A vapor pressure of 36 mm. at 0°C. has been reported by
Schlesinger and Walker (37).
The material collected in the -80° trap was be
lieved to be a mixture of dimethylboronous acid and its
anhydride. Various portions of this material exhibited
o . vapor pressures at 0 C. which were intermediate to those reported for the acid (37) and the anhydride (38). At
tempts to dehydrate this mixture failed to give pure anhydride. Direct, overnight contact with phosphoric
oxide yielded a considerable amount of methane, a small amount of trim ethylborane, and some other m aterial which was discarded. When portions of the mixture were expanded through phosphoric oxide for short periods of time, a small amount of methane was obtainedj however, the condensables usually exhibited vapor pressures which were higher than that expected for the anhydride. Attempts to fractionate the condensables failed to yield pure anhydride. From these results it was concluded that a mixture of acid and -3 1 -
anhydride exhibits positive deviation fromRaoult's Law.
One sample of the mixture which was first treated
with Dehydrite and then phosphoric oxide had a vapor
pressure of 120-122 mm. a t 0°C. (dimethylboronous anhy
dride has a vapor pressure of 119.0 mm. at 0°C.(38)).
An infrared spectrum of this sample (Appendix A) showed
that the acid was present; bands not attributed to the
acid are believed to be those of the anhydride. One
would expect from the spectra of two such related com
pounds to be similar.
g) Discussion. The fact that trimethylborane and
isopropanol do not readily yield methane whereas a
solution of isopropanol and acetic acid react with tri methylborane to yield quantitatively one mole of methane
per mole of trimethylborane used, leads to the conclusion
that the acetic acid is directly involved in the formation
of methane. This conclusion is supported by the fact that
trimethylborane reacts with acetic acid in the absence of
alcohol to produce methane. Thus the first step in the reactions described in this section appeared to be the follow ing:
Presumably the trimethylborane adds to the double bond of the carbonyl group to form the activated complex which then I
-32-
splits off methane. Further evidence for the occurrence
of reaction (l) is the isolation of diethylboryl acetate
from the reaction of triethylborane and acetic acid (5).
In the presence of an alcohol (or water) the acetate
undergoes alcoholysis (or hydrolysis) according to
reaction ( 2).
(CH3 )2B-0-£CH3 + ROH >(CH3)2B-0-R + CH3COOH (2) 0 Since the acetic acid is regenerated by this reaction,
it is thus possible to alcoholate trimethylborane by
adding only a small amount of a c e tic acid and thereby
simplify the purification of the product.
In the preparation of dimethylboronous acid there is
a third reaction possible. The acetic acid may be re
generated by the action of the boronous acid on the acetate
as indicated by reaction ( 3).
(ch3)2b-o-§ch3 + (ch3 )2b oh — * (ch 3)2b -o-b (ch 3)2 + ch3cooh ° (3)
This would explain the presence of the anhydride in the
preparation of the acid.
When trimethylborane reacts with acetic acid in the
absence of alcohol more than one mole of methane is formed
per mole of trimethylborane. This suggests a further
attack by the acid as indicated by reaction ( 4.).
(CH3)2B-0-flCH3 + CH3C00H— > CH^ + CH3B(0-fi-CH3)2 (4) 0 0
When the mono-acetate is formed in the presence of alcohol -33-
the corresponding alkoxydimethylborane is formed by re
action ( 2) and this undergoes no further attack by acetic
acid. That the acetate should react with acetic acid but
the alkoxydimethylborane not react with acetic acid is
consistent with the electron donating properties of the
groups. Thus the methoxy-group may be expected to donate
a share of electrons to the boron sufficient to block the
addition of the boron to the double bond of the carboxyl
group whereas the acetate group would not be as effec
tiv e .
Along the same line of thought one would expect that
in the case of the dimethylborylmethylperoxide the electron
donating properties of the peroxy-group would also be
sufficient to prevent attack by acetic acid and thus there
should be no interference with the quantitative determina
tion of the peroxide with the sodium iodide test solutions.
In the reaction of the trimethylborane with the
acidified solution of iodine in isopropanol, the loss of
iodine along w ith the form ation of methane in an amount
less than the 1:1 mole r a tio to trimethylborane suggests a competition between iodine and acetic acid toward re action with trimethylborane. IV. PREPARATION AND PURIFICATION OF TRIMETHYLBORANE
The trimethylborane used in these investigations was prepared from time to time by the action of methyl
Grignard reagent on boron trifluoride in n-butyl ether under a nitrogen atmosphere (39). The„trimethylborane was purified by the formation and purification of the ammonia adduct and subsequent regeneration of the tri methylborane by treatment of the purified adduct with hydrogen chloride. A typical preparation is described below.
A. Preparation of Trimethylborane
Technical grade n-butyl ether was distilled, dried over sodium, and put through a silica gel column to re move peroxides. Eastman white-label methyl iodide and
Matheson tank boron trifluoride were used without further purification. Tank nitrogen was passed through a puri fication ,train to remove water vapor and oxygen. A 3 l i t e r , 3 necked fla s k was f it t e d by means of ground-glass joints with a mercury seal stirrer, reflux condenser, thermometer, a dropping funnel and inlet for the intro duction of nitrogen. Two traps equipped with stopcocks were connected in series to the top of the condenser by means of ground-glass jo in ts . Seventy-two grams (3 moles) of magnesium turnings and 250 cc. of n-butyl ether were introduced into the flask and a slow nitrogen flow started.
—34-— -3 5 -
A solution of 426 g. (3 moles) of methyl iodide in 500 cc, of n-butyl ether was then added slowly through the drop ping funnel with stirring over a period of two hours.
The temperature of the reaction mixture was kept below
4-0°C. during the addition by cooling the reaction vessel in an ice-water bath. When addition was completed the reaction flask was cooled to -10°C. by a slush of calcium chloride and ice water and the traps were immersed in dry ice-acetone baths. A freshly made solution of 61 g.
(0.9 mole) of boron trifluoride in 400 cc. of n-butyl ether was then added through the dropping fu n n el. The addition was made over a period of about two hours main taining the temperature of the reaction mixture below 20°C. during this time. When addition was completed, the bath temperature was raised to 70°C. for two hours to complete the reaction and distill the trimethylborane, BCCH^)^, out of the reaction mixture into the traps. Practically the entire amount of trimethylborane was found in the first trap. The traps were then connected to the vacuum system and the impure trimethylborane fra ctio n a ted through a trap at -118°C. and stored in a vacuum a t dry ice-aceton e temperature until preparation of the ammonia addition com pound. Yields up to 90 per cent of crude product, based on boron trifluoride, were obtained. -3 6 —
B. Trimethylborane-Ammonia Adduct
To aid in purification and to obtain a substance
for convenient storage, the trimethylborane was converted
to the ammonia adduct, according to the
following procedure:
A measured quantity of trimethylborane was trans
ferred in a vacuum to a 500 ml. bulb. Verkamp tank-grade
ammonia was condensed in a cold tube and subsequently
introduced into the vacuum system and degassed. A slight
excess of ammonia over a 1:1 molar ratio was transferred
into the bulb containing the trimethylborane. The bulb
was then left overnight packed in dry ice-acetone slush.
The next day the bulb containing the white crystalline
ammonia adduct was evacuated at -12°C. to remove volatile
impurities. The adduct was then sublimed into a 250 cc.
evacuated bulb which had been previously weighed and the
adduct was stored at room temperature.
C. Regeneration from the Ammonia Adduct
The regeneration of trimethylborane from the ammonia
adduct was accomplished by adding a deficiency of anhydrous hydrogen chloride in a cycling system. About one quarter
of a mole at a time was regenerated in the apparatus
shown in Figure Anhydrous hydrogen chloride gas was prepared by the action of concentrated sulfuric acid on sodium chloride in another part of the vacuum system.
The hydrogen chloride was condensed in the storage tube -3 7 -
HCI measuring bulb
HCI storage
vacuum
Manometer
Disposal Circulating tube pump
vacuum BMe3 NH3 Weighing bulb
Trap Trap Reac to r
Fig. 4. Schematic Diagram of Regeneration System -38- which was immersed in liq u id n itrogen .
Trimethylborane-ammonia was sublimed from the weighing bulb into the reactor by filling the cold finger with liq u id nitrogen. The amount of ammonia adduct used was determined from the loss in weight of the weighing bulb and the amount of hydrogen chloride required was ca lcu la ted . k 10 per cent deficiency of hydrogen chloride was measured out in the measuring bulb which had previously been cali brated.
After introducing enough hydrogen chloride into the cycling line to give 10 to 30 mm. pressure on the mano meter, the reactor was opened and the circulating pump a ctivated and trap B was immersed in dry ice-a ce to n e. The rest of the hydrogen chloride was introduced into the cycl ing system in successive steps. The pumping was usually continued overnight. Since some of the adduct was en trained and condensed into trap B, it was necessary from time to time to recondense the material in the reactor.
This was accomplished by cooling the reactor with liquid nitrogen and allowing trap B to come to room temperature.
The trimethylborane was finally distilled from trap B in to trap k by immersing trap B in dry ice-acetone and cooling trap B with liquid nitrogen.
The regenerated trimethylborane was fractionated using three traps. The first trap was cooled to -118°C., the second to -142°C. and the third with liquid nitrogen. -3 9 -
The fractionated, regenerated trimethylborane collected in the second trap was stored in a five-liter bulb equipped with a mercury-protected stopcock.
D. Purity
An infrared spectrum was made of a sample of the fractionated, regenerated trimethylborane in a 9.5 cm. gas cell at 100 mm. and 10 mm. pressure. The spectrum obtained agreed with that reported by Stewart (4.0).
From time to time the vapor pressure of the tri methylborane was measured near -23°C. and the measure ments were usually within experimental error of that calculated from the vapor pressure equation given by
Furakawa and Park (4-1). V. INVESTIGATION OF THE EXPLOSION LIMIT
The experiments described in this section have been
divided into two groups - Preliminary Explosion Limit
experiments (PEL) and Explosion Limit experiments (EL).
The purpose of the PEL series was to chart the region
where the non-explosive reaction could be studied and to
observe the effect of several of the variables. The EL
series was directed to the establishment of the relation
ship between the partial pressures of oxygen and tri
methylborane and the explosion lim it. The procedures
used for the two groups will be discussed separately;
however, it will be convenient to discuss the results as
a single unit.
A. Preliminary Explosion Limits
1, Apparatus
The preliminary explosion limit studies were conducted
in the apparatus shown in Figure 5. The reaction vessel
and oxygen measuring bulb were constructed from bulbs of
similar size. During the course of the investigations two
different sizes were used. For the series PEL 1 through
PEL 10 and PEL A0 through PEL 87, the bulbs were constructed
from 250 cc. flasks which were approximately 8 cm. in diameter. The series PEL 11 through PEL 39 were performed
in vessels made from 50 cc. flasks with approximately 4*5 cm. diameter. Pressures in each bulb were measured with
—40— -41-
To vacuum manifold t t t
r supply bulb
To 0? tank
V. p. bulb
I f Reaction measuring 0 2 supply bulb I \ vessel V bulb ,
□ Hg Thermostat bath Hg manometer
Fig. 5. Schematic Diagram of Apparatus for Preliminary Explosion Limit Experiments. -42- mercury manometers. The oxygen supply bulb was con structed from a 1 liter flask. It was filled from a
Linde tank of U.S.P. grade oxygen by allowing the gas to flow through a trap containing glass beads and cooled with Dry Ice-acetone slush. In each filling the bulb was thoroughly flushed with oxygen before the supply sample was taken.
In some of the experiments in the 4*5 cm. diameter bulb, air was used as a source of oxygen. The air storage bulb contained Drierite and A.scarite for the removal of water vapor and carbon dioxide from the air.
The drying time for the air was varied from several days in early experiments to thirty minutes in the later ones.
The thermostat consisted of an appropriate liquid equipped with stirrer and thermometer. For the series pel 1 through PEL 39 an ice-water bath (0.0 1 0.2°C .) was used. For the series PEL 40 through PEL 74, Dowanol-
33 B was the liquid used and it was maintained within the selected temperature range (-30 * 1 ° C . ) by the occasional addition of dry icej the temperature was determined with a sulfur dioxide vapor pressure thermometer. For the series PEL 75 through PEL 87 a water bath (25 * 1°C.) was used.
2• Procedure
Trimethylborane was transferred from storage to the vapor pressure bulb shown in Figure 5 where i t was kept -4 3 -
at -80°C. The trimethylborane was expanded from this bulb
into the reactor until the desired pressure was attained^
then the reactor was closed and the trimethylborane in
the connecting lines was condensed back into the vapor
pressure bulb. k preselected oxygen pressure in the meas
uring bulb was obtained by allowing more oxygen to flow in
from the supply bulb or by removing some by partial evacua
tion. A.fter the desired pressure was obtained, the
temperature of the thermostat was read and then the stop
cock between the reaction bulb and the oxygen bulb was
rotated through 180 degrees. This allowed part of the
oxygen in the measuring bulb to flow into the reactor in
a short interval of time. The pressures were read and
the amount of oxygen admitted was calculated from the
pressure drop in the measuring bulb and the ratio of the
volume of the reactor and oxygen measuring bulb. Non-
condensable products were pumped out through a U trap
immersed in liq u id nitrogen. Products condensable in
liquid nitrogen were collected until they could be con veniently examined. Between experiments the reactor was evacuated 5 to 10 minutes.
Starting with PEL 40 'the procedure was modified s lig h t ly . The U-shaped manometer on the oxygen measuring bulb was replaced by an open-end manometer so th a t each pressure measurement required only one reading in addition to the zero pressure reading. Since the reaction vessel -4-4- manometer was constructed from 2 mm. bore ca p illa ry tubing
and the mercury had a tendency to stick because of inter
actio n with the rea ctio n products, t h is manometer was used
only for final pressure measurements. The initial pressure
of the trimethylborane was obtained from the manometer
or the condensation train submanifold and the trimethyl
borane was stored in one of the condensation traps rather
than the vapor pressure bulb.
The experimental data for these experiments are given
in the Appendix C.
B. Explosion Limits
a) Reaction system. Explosion limits were deter- o mined at -2 0 .4 and +20.1 C. in the apparatus shown in
Figure 6. The reaction vessel and the oxygen measuring vessel were constructed from 250 cc. flasks which had an
approximate diameter of 8 cm. They were located in sid e a
stainless steel Dewar vessel which was fitted with a stain less steel cover as indicated in Figure In order that
the working volume of the Dewar vessel could be partially evacuated, the connections between apparatus inside the
Dewar vessel and that outside were sealed at the cover plate by the use of 0-rings. By extending the mercury seal cup and shaft of the stopcocks so that they could be turned outside the bath, the oxygen and trimethylborane could be both maintained at bath temperature before mixing. The To O9 tank
To vacuum To vacuum
Gas sampling 0 2 supply bulb McLeod tube — ■ gauge vacuum Photo tube Sub -manifold housing.. To first \ trap on condensation Air tra in Vacuum
Product B(GH3 ) 3 supply tube fractionation Toepler pump tra p s
0 2 Reaction measuring vessel 1 1 bultr ------a Constant temperature bath
Figure 6. Schematic Diagram of Explosion Limit Apparatus -4 6 - details of the seal at the cover plate for one of the stopcocks and the photo tube are shown in Figure 7.
Each retaining ring was held down by three screws placed
symmetrically around the ring. Tubing of connecting lines was sealed to the cover plate in a similar manner.
The trimethylborane supply bulb was a standard vol ume (217.2 cc.) and was used to calibrate the following volumes: the connecting line between the supply bulb and the rea ctio n v e ss e l including the manometer (119.1 cc. at zero pressure), the reaction vessel (275.5 cc.) and the oxygen measuring bulb and manometer (337.9 cc. through
EL 66j 337.3 cc. after repairs following EL 66 - both at zero p ressu re). The volume increase in the manometer at a pressure p (cm) is given by the expression:
= ap (cm .) where vm is the manometer volume in c c ., a = 0.251 cc./cm . for the oxygen measuring bulb manometer and a = 0.233 cc./cm. for the “connecting line manometer,"
For the detection of radiation given off during an explosion a Farrand Electron Multiplier Photometer em ploying a GL » IP - 21 phototube was used.
The oxygen supply bulb was constructed from a 1 liter fla sk and was f i l l e d in the follow ing manner: the oxygen supply bulb, the trap and Tygon tubing leading to the oxy gen tank were evacuated then the trap was isolated from the supply bulb and cooled with liquid nitrogen. Oxygen -4 7 -
Photo tube housing
Brass retaining
O -ring — ' Stainless steel cover plate Brass adaptor
P yrex tube
Mercury
— -Block paper
R eaction vessel
Fig. 7. Cross Sections of Stopcock and Phototube Mountings!. manometer
Vacuum regulator and thermostat vacuum Trap
Condenser
Pulley
if] Vacuum Bearing ')) jacketed housing connecting tube
Freon
s o 2 y Vapor pressure thermometer
To fore pump
Stainless steel Dewar vessel
Fig 8. Diagram of Temperature Control System. -4 9 - from the tank was condensed in the trap until a suffici ent amount had been collected. The trap was then opened to the supply bulb and the oxygen distilled into it by gradually lowering the nitrogen bath. The first third of the oxygen in the trap was allowed to flow through the supply bulb and out a tube immersed in mercury which had previously been attached at the ^ 10/30 joint and evacu ated. The middle portion of the distilled oxygen was isolated in the supply bulb near atmospheric pressure and the remaining portion allowed to escape from the trap by removing the Tygon tubing.
The Toepler pump was constructed from 500 cc. and
1 liter flasks and a three-way vacuum-cup stopcock which had been altered by having a tube added to the vacuum cup.
The gas burette atop the Toepler pump was made from a 10 cc. graduated pipette to which four bulbs had been attached in series. The pipette, the connecting tubing between the bulbs and the entrance line of the Toepler pump were made from tubing of the same diameter. On the connecting tubes between each of the bulbs a line was scribed and the volume between lines calibrated by weighing the amount of mercury necessary to fill the volume. The volumes of the 10 cc. pipette plus successive bulbs were found to be 22.37, 36.02,
49.85 and 63.05 cc.
b) Temperature control. Temperatures for these ex periments were maintained in the apparatus shown in -5 0 -
Figure 8. The explosion limit apparatus (not shown) was sealed in the stainless steel Dewar vessel which had a working space 9 inches in diameter and 16 inches deep and contained approximately 2 gallons of Freon-11. In opera tion the condenser was filled with a slurry of Dry Ice and acetone and the trap was immersed in a sim ilar bath.
With the aid of the mercury manometer, the vacuum regula tor (Eck and Kreb No. 4402) was set to maintain the desired pressure. As the pressure drops in the Dewar vessel the Freon-11 (b.p. 23.7°C.) vaporizes, is condensed in the condenser and returns to the Dewar vessel. The process causes a continual lowering of the temperature until it stabilizes near the temperature at which the
Freon-11 has a vapor pressure equal to the regulated p ressu re.
The stirrer was supported from a housing located on the Dewar vessel cover. The housing was approximately
4-3/4 inches high and 2 inches in diameter except at the bottom where it was flanged to permit attachment to the cover plate. The shaft was held firmly in place by two pairs of bearings - one pair located at the top of the housing and the other near the bottom. Below the lower pair of bearings were two Garock No. 51 x 87 Klozures which fitted tightly against the 5/8 inch stirrer shaft, sealing it against leakage. An 0-ring recessed into the cover plate pressed against the lower Garock Klosure and completed -5 1 - the seal of the stirrer shaft and cover plate. The top of the Dewar vessel carried a polished face plate against which was pressed the O-ring fitted in a groove in the bottom of the stainless steel cover plate. The stirrer shaft was driven by a quarter horsepower motor through a pulley-belt system which gave a 6:1 speed reduction.
When the system was operated at a bath temperature of 20.1°C. it was found that the higher pressure setting on the vacuum regulator was very sensitive to changes in room temperature and it became necessary to thermostat the vacuum regulator for proper control. This was done by placing the regulator in an air box equipped with s t ir r e r , thermometer, Fenwal Regulator (Model 17500), a
110-volt relay and a 25-watt bulb as a heater.
c) Temperature measurement. For the experiments at
-20.4°0. a sulfur dioxide vapor-pressure thermometer was used and the temperature was measured by comparison of the vapor pressures of sulfur dioxide obtained with those quoted by Sanderson (32).
For those experiments at 20.1°C. the temperature was determined with the aid of a platinum resistance thermometer, the resistance of which was determined by the potentiometric method (4-2). The platinum resista n ce thermometer was con nected in series with a standard resistor and a current of
2.8 milliamps. maintained through the circuit. With the aid of a Leeds and Northrup Portable Precision -5 2 -
Potentiometer Model No. 8662, the voltage across the ther
mometer and standard r e s is to r were measured three tim es in
rapid succession in order to eliminate error due to change
in battery current. When constant readings were obtained,
the resistance of the thermometer was calculated with the
following equation:
EPt RPt = RS
where Rpt = resisStance of the platinum thermometer
Ept = voltage across the platinum thermometer
Eg = voltage across the standard resistor
Rg = resistance of the standard resistor (24..984O ohms)
From the resistance of the platinum resistance thermometer,
the temperature was obtained by use of a table which had
been constructed from the following equation:
Rt = Rq + cRq + cRo£i(t/l00 - 1) t / i o o ]
where R^ = resistance of thermometer at temperaturet°C.
Rq = resistance of thermometer at 0°C. (25.507 ohms - measured with Mueller Bridge), c = constant (0.00392557 - from previous calibration)
$ = constant (1.492 - from previous calibration).
A small supply of trimethylborane was stored in the
supply tube (Fig. 6) which was usually kept in a Dry Ice- acetone bath. At the beginning of an experiment the reaction vessel was evacuated to lO”^ cm. or less for a -5 3 -
period of at least 5 minutes. Trimethylborane was intro
duced by expanding it from the supply tube into the reactor
and connecting line. With the supply tube closed, the pressure in the reactor and connecting line was measured by means of the manometer attached to the connecting lin e .
After the pressure measurement was obtained, the reactor was closed and the trimethylborane in the connecting line was condensed back into the supply tube by use of liquid nitrogen .
The oxygen pressure in the measuring bulb was ad
justed to a desired value by admitting more oxygen from
the oxygen supply bulb or by partial evacuation. The pressure was then measured with the attached manometer.
In order to insure temperature equilibrium the mixing of the gases was delayed for 5 minutes.
After opening the shutter to the phototube and ob taining the background reading, the stopcock between the reactor and the oxygen measuring bulb was rotated through o 180 and the stopwatch started. (The rotation of the stop cock allowed a portion of the oxygen in the measuring bulb to enter the reactor in a short interval of time.) Ex plosions were detected by a deflection of the galvanometer in the phototube circuit. Both the magnitude of the de flection and the time from the rotation of the stopcock were noted. If no deflection occurred within 60 sec., the experiment was considered a non-explosion. -5 4 - Measurement of the oxygen pressure in the measuring bulb after completion of the experiment allowed calcula tion of the initial oxygen pressure in the reactor. The following equations were used for these calculations:
PR = 337.9(P0o 2 - Pk02 )+0.25l(Pn 02 - ? 0 ' 2 ' ) (For EL 00 °2 — • through EL 66) p 337.3(Pq - Pi )+0.251(P« - P'2) Ilf) 2 2 2 Oo 2 = ------=- .(After EL 66) 275.5 where P-r, = initial oxygen pressure in reactor 2
Pn = initial oxygen pressure in measuring bulb 2
P1 = final oxygen pressure in measuring bulb. °2 For those experiments in which explosion did not occur, the reactor was opened to the first trap of the condensation train by way of the submanifold. The trap was immersed in liquid nitrogen and opened to the vacuum pumps. Thus only the condensable products were c o lle c te d .
Products collected in this way were transferred into an iodometric test solution (see Section III-E-4-2) in order to destroy the peroxide present.
After experiments in which an explosion occurred, the reactor was opened to the "connecting line" and the pressure read on the manometer. From the reading the final pressure -5 5 - in the reactor was calculated by means of the equation
p 394.5P2 + 0.233 P2 R ------275.5 where P^ = final pressure in reactor
P2 = pressure in reactor and connecting line including manometer.
The handling of the explosion products was rather varied. In general the products were transferred in the product fractionation traps which were at -80, -118, - 14-2 and -196°C., respectively. The non-condensables were pumped out, sometimes with the Toepler pump and other times w ith the vacuum pumps. The non-condensable and
fr a c tio n (that c o lle cte d at -196°C .) were the major fractions. During some series of experiments the products from the series were collected in an attempt to identify constituents of the various fractions. Analyses were made on the products of four explosions at -20°C. which were near the explosion limit.
C. R esults
1 * Mature of the Explosion
The explosions were characterized by a rise in press ure except for high mole-fractions of oxygen and a flash of light. In some instances a sharp "ping" was also heard.
Flashes observed in the preliminary explosion limit experi ments were usually bright greenj however, in one particular experiment a bright blue-white flash was observed. The 56 explosions also produced an apparently non-volatile solid which, after the course of repeated experiments, produced a grayish-white coating with considerable variation in shading and th ick n ess.
2. Relationship of the Partial Pressures of Trimethvl-
borane and Oxygen at the E xplosion Limit
In Figures 9, 10, 11, 12 and 13 are the results of the determination of explosion limits in an 8 cm. diameter bulb at 25, 20,1, 0, -20.4 and -30°C., respectively. The limits of the EL series (Figs. 10 and 12) were more ex tensively studied and clearly show that a plot of the reciprocal of the trimethylborane pressure against the reciprocal of the oxygen pressure gives a straight line for the boundary between the explosion region and the non explosion region. Thus the general relationship between partial pressures of the reacting gases and the explosion limit is given by the expression
This same relationship has been applied to the limits of the PEL series (Figs. 9, 11, 13)j although the data are not sufficient to be conclusive, nevertheless, the relation ship appears to be applicable. There appears to be some scatter in the dataj however, this is not surprising con sidering the possible variation of mixing, concentration and flow gradients and the competition from the "slow” rea ctio n . - 5 7 -
• Explosion 2 8 ° Non-explosion
2 4
20
Explpsion region
0 2 4 6 8 10 12 I 0 2
P o 2 (mm.)
Fig. 9. Explosion Limit of Trimethylborane and Oxygen in an 8 cm. Diameter Bulb at 25°C - 5 8 -
32
o Non - explos ion • Explosion D BMe3 as Me2BOOMe 28 non-explosion
24
20
Explosion region o
P (mm)
Fig. 10. Explosion Limit of Trimethylborane and Oxygen in an 8 cm. Diameter Bulb at 20.I°C. -5 9 -
2 8
• Explosion -• Explosion in clean bulb 2 4 o N on-ex plosion o - N o n - e x p lo s io n in clean bulb
20 o-
I 0 ‘ ^B M ej (mm.)
Explosion region
0 2 4 6 8 10 IQ2 PO2 (mm.)
Fig. II. Explosion Limit of Trimethylborane and Oxygen in an 8 cm. Diameter Bulb at 0°C. -60-
E xplosion Explosion in clean bulb o Non-explosion o-Non-explosion in clean bulb O BMe3 mainly as Me2BOOMe Non - explosion
o o o o
10' P B M e* frnm.)
Explosion region
POo (mm.)
Fig. 12. Explosion Limit of Trimethylborane and Oxygen in an 8 cm. Diameter Bulb at -20.^C. 2 4
• Explosion - • Explosion in clean vessel o Non-expbsion 20 o - ONon-explosion in clean v e s s e l
• •
Explgsion region
0 2 4 6 8 10 12 IQ2 P 0 2 (mm.)
Fig. 13. Explosion Limit of Trimethylborane and Oxygen in an 8 cm Diameter Bulb at ~30°C. -62-
The values of a and b o'btained from the different graphs are given in Table 3. The significance of the values obtained will be interpreted in the discussion of the r e s u lt s .
TABLE 3
VALUES OF THE "CONSTANTS" IN THE EXPLOSION
LIMIT EXPRESSION
Temperature a b °G. (mm.”1 )
25 0.312 2.12
20.1 0.309 2.43
0 0.294 2.82
0 .189 a 2.45 8
-2 0 .4 0.284 2.86
-30 0.258 3.10
a For 4.5 cm. bulb diameter.
At lower temperatures it appears that deviation from the above relationship is encountered at low trimethyl- borane pressures (Fig. 13).
From the graphs in Figure 14 explosions occur more readily for trimethylborane-oxygen mixtures in which the mole-fraction of oxygen has a value near 0.6. Thus mix tures with trimethylborane to oxygen ratios of 2:3 or 1:2 appear to be the most explosive.
In addition to these results, it is of interest to consider two special experiments, EL 119-P and EL 170-P. Total 70 60 40 30 20 50 0 i. 4 Vrain f oa Pesr wt Mole-fraction with Pressure Total of Variation 14. Fig. Explosion # a Non- explosion] Non- a 0.2 of Oxygen for Explosion Limits in 8 cm. cm. 8 in Limits Explosion for Oxygen of imtr ub t 2. ad 20.1°C. and -20.4 at Bulb Diameter oetatin f oxygen of ion Mole-tract 20.l*G.
63- 3 -6 0.4 jExplojsion region ; 0.6 8 0 1.0
30
ajnssajd ajnssajd 10401 ) ( j u u u -6 4 -
Each of these experiments was performed by adding oxygen to the products of a non-explosive experiment and has been plotted as if no reaction had occurred in the initial ex periment. The results are given as squares in Figure 12
(EL 119-P) and Figure 10 (EL 170-P) and it is evident that the product of the "slow" reaction (dimethylborylmethyl- peroxide) is not equivalent to the unreacted gases as far as the explosion limits are concerned. If in these ex periments one treats the dimethylborylmethylperoxide as an inert gas or as being equivalent to the same pressure of trimethylborane, then the experimental points are well within the non-explosion regions.
3. Effect of Surface
a) Change in limit with vessel size. In Figure 15 is shown the data for the explosion limits in a 4.5 cm. diameter bulb at 0°C. From comparison of these results with the limit in an 8 cm. diameter bulb at 0°C. it is obvious that the increase of the surface to volume ratio requires higher pressures for explosions. This infers that the explosion process is a chain process which terminates on the wall.
b) Surface conditioning. In several of the graphs of the explosion limit points have been plotted for experi ments in clean vessels. Although these points are rather meager, those in Figufe 12 indicate that any effect of product coating on the walls has only slight if any effect -6f>~
20
o-
o -
C r O
O Pxlso • m CPExplosion
♦ Explosion -• Explosion irt clean bulb O Non-explosion Non-explosion in cledn butb
0 2 4 6 8 10 12 10? P 0 2 (mm.)
Fig. 15. Explosion Limit for Trimethylborane and Oxygen in a 4.5 cm. Diameter Bulb at 0°C. -66- on the limits. Thus it appears that a coated wall is no more effective in breaking chains than a clean wall.
4. Effect of Temperature
In Figure 16 the limits in an 8 cm. diameter bulb at various temperatures are shown. (The curve for 0°C. was omitted since it is rather poorly defined and believed to be less reliable than the others.) It is noted that explosions occur at lower pressures as the temperature is raised. Since an increase of temperature decreases the concentration for a given pressure, it is evident that increasing the temperature increases the rate of branching by an amount sufficient to off-set the decrease in concen tration at a given pressure.
5• Effect of Added Hitrogen
The results from the PEL series in which dry air was used as a source of oxygen are given in Figure 17. The data are insufficient to give the shape of the limit; however, it is definite that addition of nitrogen raises the pressures necessary for explosion. A more extensive study was made in an EL series in which a mixture of nitrogen and oxygen (PN = 0.305P02) was used as a source of oxygen. The results of this study are shown in
Figure 18. At the higher oxygen pressures and thus for greater addition of nitrogen, higher pressures are needed for exp losion as compared to experim ents with no added nitrogen. At lower pressure the results are not decisive. -6 7 -
32
2 8
2 4
20
+ 2 0 .
" 20.4*
0 2 4 6 8 10 12 IQ2 PO 2 (mm.)
F ig . 16. E ffect of Tem perature on t h e E xp losion L im its in an 8 cm. Diameter Bulb. -6 8 -
« Explosion 2 0 O Non-explosion
Y \ 16 \ —Explosion limit with pure oxygen \ ...... \ : \ ' ' ...... o \ o PBMe3 (mm.) o o o° \ 8 .. \ . . \ \ • \ 4 \ \
\ \ 0 2 4 6 8 10 IQ2 P(I>2 (mm.)
Fig 17. Explosion Limit of Tri methyl borane and Oxygen in a 4.5 cm. Diameter Bulb at 0°C. Using Air as a Source of Oxygen. -69-
20 • Explosion -» Explosion jn clean bulb o - o Non-explosicin o-Nop-explosion in 24 clean bulb Limit for -20.4®C. no nitrogen present 0.305 R 20
o
O:
2 4 6 8 100
POg (mm.)
Fig. 18. Explosion Limit of Trimethylborane and Oxygen—Nitrogen Mixture in an 8 cm. Diameter Bulb at ~20.4°C. This type of inert gas effect suggests either a third-
body homogeneous destruction of chain carriers or possibly
a third-body process that interferes with the branching
process.
6. Products of Explosions
a) Identification of volatile products. As mentioned
in Section V-B-2 the products from the EL series were
generally fractionated through traps at -80, -118, -142,
and -196°C. This yielded five fractions - A, non-condens-
ables which passed through -196°C.; B, collected at -196°C.
(sometimes referred to as the C£ fraction); C, collected
at -142°C.; D, collected at -ll8°G.j and E, collected at
-80°C. Fractions A. and B were always the major fractions
and only small amounts of material were obtained in frac
tions D, E, and F. With the aid of gas phase chromato
graphy Fraction A was found to consist of hydrogen, methane,
carbon monoxide, oxygen and occasionally traces of nitrogen
apparently present in the oxygen used; likewise fraction B
was found to consist of ethane, ethylene, acetylene and
carbon dioxide.
During the e a rly work l i t t l e was done w ith fra ctio n s
G, D and E due to their smallness (individual fractions of
single explosions usually less than 0.01 mmole). The
first observations were made on samples which had been ac
cumulated over a number of explosions. Generally these products caused little if any coloration of sodium iodide - 7 1 -
test solution, thus indicating that little or no peroxide
was present. It was also observed that fraction E on
standing at room temperature produced methane, indicating
decomposition or reaction of the constituents of this
fraction. Because of this reactivity later samples of . o fractions C, D and E were maintained at -80 until measure
ments were made. In v estig a tio n of these fra ctio n s was
limited to determining the size of the fraction (in some
individual cases) and obtaining the maS3 or infrared
spectrum of the fraction.
The interpretation of the mass spectral data is
illustrated in Table 4. The observed spectrum is for the
combined C and D fractions of products accumulated over a
series of explosions and may contain material from the E
fraction due to entrainment. The normal procedure for
interpretation was to assign one of the higher peaks to
some p articu lar compound, ca lcu la te the to ta l con trib u tion
of that compound by using the relative intensities listed
in Appendix A and then select a lower.peak and repeat the
process. Contributions ascribed to trimethylboroxin were
based on the peak M/e = 111, those of dimethoxymethyl- borane on M/e = 73 and those of methoxydimethylborane on
M/e = 57. In regard to these interpretations one should keep in mind that changes in operating conditions may cause changes in the cracking patterns (usually changes between groups, not within a group), failure to achieve and - 7 2 - TABLE 4.
INTERPRETATION OF MASS SPECTRUM OF EXPLOSION PRODUCTS
Observed Peak Height Contribution from Residual P e a k ------Peak M/e Height (ch3bo) 3 CH3B( och3 )2 (CH3)2BOCH3 Height
_ 12 94 94 13 64 18 2 — 44 14 175 32 5 23 115 15 1149 155 96 650 248 16 67 25 - — 42 17 63 -- - 63
23 13 __ 13 24 63 13 - - 50 25 172 42 7 35 88 26 399 100 9 70 220 27 370 44 11 97 218 28 1452 182 22 106 1142 29 706 62 33 186 42 5 30 94 4 90 31 226 17 21 188 32 142 - 2 12 128
36 150 — 27 123 37 441 14 - 70 357 38 332 47 27 258 39 731 36 — 74 621 40 405 105 3 46 251 41 654 178 7 104 365 42 641 282 40 70 249 43 1159 190 136 143 690 44 398 234 3 — 161 45 182 8 6 — 168 46 24 - — • m 24 47 28 — — — 28 48 106 - - _ 106 49 395 - - 395 50 985 8 - 977 51 663 2$ — 638 52 632 60 mm mm 572 53 177 85 3 mm 89 54 157 167 2 mm -10 55 318 8 9 66 235 56 611 10 30 530 41 57 2160 - 90 2070 -73-
TABLE 4 (continued)
Observed Peak Height Contribution from R esi Peak & Peak Height (CH3B0)2 CH3B(0CH3 )2 (CH3)2B0CH3 Heig
64 - 4 46 14 82 — 10 — 72 65 - — mm 65 218 — — mm 218 36 — mm 36 127 - - - 127
55 _ 55 74 12 - 62 155 93 — — 62 540 370 - — 170 713 523 — 190 8 -8 21 —— 3 18 103 — 100 7 -4 408 — 408 — 85 - 10 — 75 133 8 — 125 85 — — — 85 330 — — 330 1223 —— •» 1223 829 — mm 829 10 mm — mm 10 19 8 mm 11 10 7 mm 3 16 14 — 2 26 27 -1 17 93 - -76
8 mm 2 6 6 - 8 mm -2 3 — — - 3 rr 34 34 17 - - - 17
_ 11 7 mm 3 19 13 mrn 6 16 10 mm 6 -74- TABLE 4 (continued)
Observed _ , „ . _ . ,, . . . Residual peak Peak Height Contribution from Peak M/e Height (CI^BO^ CH^ bToChJ)^ {CYL^)2'BOQ'Rj Height
99 12 99.5 20 100 28 Hg 100.5 15 101 36 102 12
108 20 19 — l 109 230 219 — - l l 110 915 894 —— 21 111 1210 1210 — _ _ 112 33 33 — _ — 113 5 - - - 5
122 22 33 -11 123 32 6 — — 26 124 28 40 — — -12 125 107 134 -_ -27 126 136 176 — — -40 127 8 7 - - 1 -75-
maintain pressure equilibrium in the instrument may cause
distortion between groups, and lastly that the assignment
of mass to individual peaks is not absolute, particularly
for isolated groups of small peaks.
The observed mass spectra for several of the explosion
product fractions are listed in Table 5 and a summary of
the interpretation of these spectra is given in Table 6.
In general those spectra in which trimethylboroxin is be
lieved to be present have low values for the peak heights
at M/e = 86 and 54-j no other peaks with appreciably low
values for the peak height were encountered. The presence
of residual peaks with appreciable heights indicate that
other substances are also present. Other than the peak at
M/e =18 which is due to water, no definite assignment
can be made for these residu al peaks with any c er ta in ty .
Some of the residual peaks are consistent with the possi
b i l i t y that some other boron containing compounds may be
present. (-The ratio of the isotopes to is approxi
mately U to 1.) Nevertheless it is not possible to rule
out the possibility that some of these peaks may be due to
hydrocarbons or oxygenated hydrocarbons.
In Figures 19, 20, 21 and 22 are the infrared spectra
of several product fractions obtained from explosions.
Because of the small size of the sample, the spectra were obtained using a small cell which did not utilize all of the sample beam and thus some loss in resolution was -76-
TABLE 5
MASS SPECTRA OF EXPLOSION PRODUCTS
Peak Heights ______EL 160______EL_i§l______EL 165 Fractions Fraction Fraction Fraction Fraction Fraction M/e C and D ECD EE
11 5 13 10 18 15 12 10 14 37 39 7 - 13 8 13 26 26 6 6 14 25 45 46 56 17 17 15 173 281 407 372 95 78 16 12 17 14 15 6 30 17 6 43 6 5 8 72 18 17 155 20 18 30 281
24 6 20 21 5 m m 25 7 17 46 55 11 6 26 16 51 38 90 44 25 27 20 43 45 68 20 17 28 50 104 41 88 40 74 29 55 148 92 104 42 65 30 10 23 6 15 7 13 31 30 112 24 40 23 60 32 18 51 12 17 11 32
36 3 6 19 2 37 11 16 44 25 9 — 38 5 9 15 77 6 11 39 14 13 34 57 18 11 40 8 39 18 117 19 24 41 23 75 31 50 34 26 42 13 101 30 82 35 52 43 27 204 71 89 55 89 44 17 36 11 163 16 33 45 3 36 19 18 8 — 46 - 5 7 12 — 5 47 *■ 13 48 20 30 2 M i 49 4 - 84 129 4 50 12 - 221 363 7 51 3 3 19 101 5 — 52 3 7 18 81 8 4 53 1 15 9 20 8 4 54 - 16 4 20 12 12 55 6 39 15 43 13 7 -7 7 -
TABLE 5 (continued)
Peak Heights EL 160______EL 161______EL..165 Fractions Fraction Fraction Fraction Fraction Fract: M/e C and D E C D E E
56 30 56 88 45 39 13 57 114 182 347 151 3 5 58 3 19 8 10 10 20 59 5 57 — 26 2 10 60 — 13 - 3 - 6 61 — 44 - 10 - - 62 — - - 5 -- 63 — - — 21 - - 64 — 5 - 6 — - 65 - - 6 5 - - 66 — 3 11 9 — - 67 — 18 — 23 12 5 68 — 59 - 81 35 17 69 - 83 — 121 50 26 70 - 4 - 2 1 - 71 -- 4 2 — - 72 8 18 1 29 3 2 73 31 72 4 119 12 74 74 - — - 20 3 - 75 -— mm 7 - - 76 - - - 17 3 - 77 —— - 62 1 — 78 — - 290 6 — 79 -- - 19 1 -
81 9 -- 82 — —— ■“ - 83 - 2 - 3 3 - 84 - 4 - 6 3 - 85 — 5 3 3 3 -
87 mm •m 88 ------
_ 91 5 am 92 — - - 3 - -
_ 94 1 mm 95 --— 3 — mm 96 2 — mm- 97 stopped stopped stopped -7 8 - T.ABLE 5 (continued)
Peak Heights EL 160______■ EL 161 EL 165 Fractions Fraction Fraction Fraction Fraction action M/e C a nd D E C 0 E E ioa 5 — - 109 53 21 10 110 221 84 39 111 309 117 53 112 9 4 2 113 3 2 -
122 3 4 2 123 6 6 4 124. 8 3 2 125 32 11 5 126 44 16 7 127 2 1 — -79-
TABLE 6
SUMMARY OF INTERPRETATION OF MASS SPECTRA
M/e for Major Experiment Fraction Constituents a Residual Peak
EL 160 C and D ch 3ob(ch 3 )2 15, 201s, 31, 4.0*8, 50, 81 (ch 3o)2bch 3
EL 160 E (ch3bo)3 15, 18, 20*s, CH OB (CH ) 31, AO’s, 61 3 3 2 (CH30 )2BCH3
EL 161 C ch 3ob (ch 3 )2 15, 20*s, 30*s, (CH30 )2BCH3b 40»s, 49, 50, 66
EL 161 D (ch3bo) 3 15, 20*s, 31, 40*s, (ch3o)2bch 3 49, 50, 51, 77, 78 CH30B(CH3 )2 b
EL 161 E (ch3bo)3 15, 18, 40‘s, 50, 56, 56, 62, 78 (CH30)2BCH3
EL 165 E (ch 3bo)3 15, 18, 20*s, 40’s, (ch3o)2bch 3 50»s
a Constituents listed in order of the magnitude of their contribution. b Contribution from these constituents very slight. % TRANSMISSION g 1. nrrd pcrm f rcin o E 168. EL of C Fraction of Spectrum Infrared 19. ig, F jfilL CONS N ICRO M
08“ % % TRANSMISSION g 2. nrrd pcrm f rcin o E 168 EL of D Fraction of Spectrum Infrared 20. ig. F 60 H oa o z % T R A g 2. nrrd pcrm f rcin o E 168 EL of E 9 Fraction of Spectrum Infrared 21. ig. F 6 0 S * " * * M6R0NS '£ N> Od % % TRANSMISSION nrrd pcrm f rcin o E 19 n E .172 EL and 169 EL of D Fraction of Spectrum Infrared i encountered. The identification of boron-containing com pounds is made easier by the fact that these compounds have bands with high extinction coefficients. The inter pretation of these spectra is summarized in Table 7.
TABLE 7
INTERPRETATION OF INFRARED SPECTRA OF
PRODUCT FRACTIONS FROM EXPLOSIONS
Experiment Fraction Interpreta tion
EL 168 C ch3ob(ch 3 )2
EL 168 D (CH^BO)^; however band nea 15 microns indicates an other substance also pre sent
EL 168 E « a (ch 3bo)3
EL 169 D Composite of (CH^BO)^ and EL 172 CH3OB(CH3 )2 also third substance indicated by band near 15 microns.
a Fraction E’ is that part of fraction E which has passed through a trap at - 64.0 used to remove water from the sample.
From the results of the mass and infrared spectral investigations, it appears that trimethylboroxin and methoxydimethylborane are the major volatile boron-contain ing products of the explosive oxidation of trimethylborane
There is some indication that dimethoxymethylborane is also formed along with small amounts of unidentified pro ducts which may or may not contain boron. -85-
b) Observations concerning the solid coating on
the wall. During the course of repeated explosions a
grayish white solid coating was accumulated on the walls
of the reaction vessel. From time to time the reactor
was cleaned and the following observations made: The
coating appeared to consist of at least two different
substances - one of which was white and the other black
or some other dark color. When the reaction vessel was
opened to the air a peculiar odor was noticed. Water
apparently dissolved the white portion but had no effect
on the black part. The rinse water had black particles
suspended in it and the ether extract of this rinse water
had a slight yellow color (some boron hydride polymers
are yellow). ifter rinsing with water the wall coating
was black. These black p a rtic le s were not read ily soluble
in water, acetone, ether, methanol or nitric acid; however, methanol seemed more effective in removing the particles
from the walls. Final removal of the black coating was effected with chromic acid cleaning solution. When some
of the black p a rtic le s were heated in a tube with oxygen flowing through it, the particles disappeared; but a white deposit appeared down stream from the heated zone.
From these observations and the fact that many of the explosions did not have sufficient oxygen for complete combustion, the possible products in the coating includes boric oxide, boric acid, boron-oxygen polymer with -8 6 - occasional methyl groups, boron hydride polymers, boron, carbon or boron-carbon polymers.
c) Analysis of the products of four explosions near the limit at 20.1°C. The results of the analysis of the products of four explosions near the limit has been sum marized in Table 8. (Gas Phase Chromatographic analysis of non-condensables and C£ fraction is given in Appendix
D.) Because of the wide variation in initial pressures and mole-fractions along the explosion boundry, the varia tion of the ratio of mmoles of product per mmole of tri- methylborane with mole-fraction of oxygen in the initial reaction mixture was considered as the most informative relationship derivable from these analyses. This relation ship for individual products is illustrated in Figure 23 and several features are readily noticeable. As the mole- fraction of oxygen is increased the relative amounts of hydrogen and carbon monoxide increases rapidly until the mole-fraction of oxygen reaches a value near 0.7 after which the relative amounts of these two products decrease rapidly. This rapid fall off is undoubtedly caused by the further oxidation of these materials or their precursors to form water and carbon dioxide. This conclusion is supported by the high yield of carbon dioxide and water
(high peak at M/e = 18 in mass spectrum of fraction E) found in the products of EL 165. The occurrence of the maximum relative yields of hydrogen and carbon monoxide - 8 7 -
TABLE 8
ANALYTICAL DATA OF EXPLOSION PRODUCTS
Experiment EL 163 EL 161 EL 160 EL 165 M ole-fraction of 02 ( i n i t i a l ) 0.441 0.561 0. 664. 0.821 mmoles of m aterial BM83 (used) 0.206 0.146 0.113 0.074 h2 0.253 0.304 0.378 0.028 CHy 0.153 0.058 0.008 0 CO 0.067 0.160 0.298 0.108 O2(recovered) 0 0 0.001 0.002 0.012 0.0026 0.0005 0 < * 2=6 0.0068 0.0011 0 c 2h4 0.037 C2H? 0.034 0.061 0.0073 0 C02 0.0029 0.0031 0.0032 0.114 F raction C 0.0066 0.032 0.0005 u#n nm uuio A Fraction D 0.0089 0.0043 0.0008 F raction E 0.0177 0.0053 0.0055 0.0053 mmoles of material/mmole of t r i methylborane used H2/BMe3 1.23 2.08 3.35 0.38 CH//BMe3 0.74 0.40 0.071 0 CO/BMe3 0.33 1.10 2.64 1.46 C2 H6 / B ^ e 3 0.058 0.018 0.004 0 C2H,/BMe3 0.180 0.047 0.010 0 C2H2/BMe3 0.165 0.418 0.065 0 C02/BMe3 0.013 0.021 0.028 1.54 F raction C/BMe3 0,032 0.022 0w * 01AUXZf 0.006 Fraction D/BMe3 0.043 0.029 0.011 F raction E/BMe3 0.086 0.036 0.049 0.072 mass balance based on non-condenS' able and C2-fractions gram atoms/mdLe of trim ethylborane ■ Hydrogen 6.82 6.89 7.18 0.76 Carbon 1.89 2.49 2.90 3.00 gram atoms/mole of oxygen used Oxygen 0.44 0.89 1.37 0.66 -88-
3.2
2.8
xi 2.4
2.0
0.5
0.8 0.4
0.3
0.4 0.2
0.1
0 0.2 0.4 0.6 0.8 1.0 Mole - fraction of oxygen
Fig. 23. Product Distribution as a Function of Mole- fraction of Oxygen for Explosion Near the Limit at 20.1°C. -8 9 - at a mole-fraction of oxygen near that at which minimum pressures for explosion occur suggests that the precursors of these two products are involved in the triggering mechanism of the explosion.
For methane, ethane and ethylene, the relative yields decrease steadily with increasing mole-fraction of oxygen and approach zero near 0.7 mole-fraction of oxygen. The parallel production of these materials suggest a common precursor, probably the methyl radical. The relative pro duction of carbon dioxide increases very slowly with in creasing mole-fraction of oxygen until the value approaches
0.7, then it increases very rapidly, presumably because of the oxidation of carbon monoxide.
Of the C2 hydrocarbons the relative production of acetylene is the largest and its relative production is quite different from the rest, increasing with increasing mole-fraction of oxygen, reaching a maximum near 0.55 mole- fraction of oxygen and then decreasing. The true signifi cance of this behavior is not really knownj however, it does lend some support to the speculation that compounds of the form „ may be involved. .o-h R-bJ\ C-H
Figure 24. is a graph of the relative mass balance obtained from the non-condensable and fractions as a function of the mole-fraction of oxygen of the initial reacting mixture. In regard to the figures on this graph i. atoms of Pr°duct/ m0|e 0f trimethylborane 2 4 8 6 0 i. 4 Rltv Ms Blne band from Obtained Balance Mass Relative 24. Fig. o odnal ad 2 Fractions. C2 and Noncondensable - 0.2 oefato o oxygen of Mole-fraction 0.4 -90- 0.6 0.8 1.0 . tm of 0 atoms g. o e f Og ofmole -91- one should keep in mind that the maximum values are 9 for hydrogen, 3 for carbon and 2 for oxygen. Below a mole- fraction of oxygen of 0.7 these two fractions (non-con- densable and C£) account for 7/9 of the hydrogen; thus under these conditions little water is formed. 4bove 0.7 hydrogen is predominantly found elsewhere as the mole- fraction increases, presumably in the form of water; how ever, practically all of the carbon can be accounted for in this region. 4s the mole-fraction of oxygen decreases from 0.6 both carbon and oxygen appear less and less in these two fractions, apparently because of the increased relative production of such compounds as trimethylboroxin, methoxydimethylborane and other oxygenated boron-organic compounds. The decrease in the accounting of oxygen as the mole-fraction of oxygen is increased above 0.7 is ob viously due to the increased relative production of water and boric oxide as complete combustion is approached.
d) Pressure change for explosions near the limit.
Pressure changes for explosions near the limit are given o in Figures 25 and 26 for explosions at -20.4 and 20.1 0. respectively. The pressure change is defined as the differ ence between the final pressure and the sum of the initial pressures of oxygen and trimethylborane. In general the pressure change is positive if the mole-fraction of oxygen for the initial mixture is below 0.8. The plot of the pressure change against mole-fraction of oxygen for the -92-
4 0
30
20
imm.)
20
0 0.2 0.4 0.6 0.8 1.0 Mole-fraction of oxygen
Fig. 25. Pressure Change for Explosion near the Limit at -20.4°C. in an 8 cm. Diameter Bulb. -93-
30
20
20
0.2 0.4 0.6 0.8 1.0 Mole-fraction of oxygen
Fig. 26. Pressure Change for Explosions Near the Limit at 20.l°C. in an 8 cm. Diameter Bulb. -94- explosions at -20.4°C . appears to have two maxima, one at
approximately 0.5 mole-fraction of oxygen and the other near 0.7. For the explosions at 20.1°C. the curve has a maximum near 0.7 and a shoulder near 0.55 mole-fraction
of oxygen. From the above section it is clear that the maxima at 0.7 mole-fraction of oxygen are due to maxima in
the relative production of hydrogen and carbon monoxide.
The shoulder near 0.55 may be due to contributions from
acetylene, in which case the maximum at 0.5 mole-fraction
of oxygen for the -20.4°C. explosion indicate that the
production of acetylene is more prevalent at the lower
temperatures. These same relationships hold true for the relative pressure changes (ratio of final pressure to
initial pressure) shown in Figures 27 and 28. An interest
ing feature of these later plots is the pressure drop noted at the higher mole-fractions of oxygen. For complete com bustion we have
b(ch3)3 + 602----» l/2B203^ + 3C02 + 4-l/2H20 and the relative pressure change should be 1.07 or 0.42 depending on whether or not the water was liquid or vapor.
From the graphs the indication is that the water is not in the vapor state. At -20.4°C. this is not surprising; however, for the experiment at 20.1°C. and 0.9 mole- fraction of oxygen, the size of the vessel, amount of material and vapor pressure of water indicate that approxi mately 90 per cent of the water should be in the vapor -9 5 -
2.4
2.0 0)u 3 ir> ua> a o c
a o c 0.8 u_
0.4
0 0.2 0.4 0 6 0.8 1.0 Mole fraction of oxygen
Fig. 27. Relative Pressure Change tor Explosions Near the Limit at -20.4WG in 8 cm. Diameter' Bulb. -9 6 -
2.4
2.0
a> l3. l/> a>to ia - o c
Z3 (/) a>L. Q. O C 0.8 u.
0.4
0 0.2 0.4 06 0.8 1.0 Mole-fraction of oxygen
Fig. 28. Relative Pressure Change for Explosions Near the Limit at 20.1°C. in an 8 cm. Diameter Bulb. -9 7 -
sta te . Thus i t appears th at the water must be bound in some way, possibly with the boric oxide in the surface coating,
For the experiments performed at -20.4-°C. in which
nitrogen was added, the pressure change (or relative
pressure change) follows the general relationship ex
hibited by those without nitrogen if the nitrogen
pressure is ignored in the calculation of the mole-
fraction of oxygen (and the relative pressure change).
k slight lowering of the curves may occur, but the
data are not sufficient to be conclusive. VI. INVESTIGATION OF THE KINETICS OF THE
REACTION BELOW THE EXPLOSION LIMIT
This section refers to the investigation of the kinetics of the reaction of trimethylborane and oxygen at pressures below the explosion limit. In this study the reaction was followed by measuring pressure changes at various times after mixing the gases at 19.9 or
-20.1°C. in one of two reaction vessels.
All kinetic experiments concerning the reaction of trimethylborane and oxygen at pressures below the ex plosion limit are designated by the prefix "K" . These experiments are numbered consecutively except for those reactions in which oxygen is added to the products of a previously performed experiment; these latter experi ments are designated by the suffic "P". Thus K-S-P designates the experiment performed by adding oxygen to the products of experiment K-8.
A. Apparatus
1. The reaction System
The reaction system was similar to that use in the explosion limit experiments except for the addition of a pressure measuring device to the reaction vessel.
Figure 29 is a schematic diagram showing the modifica tions made in the system to include the pressure trans ducer and Figure 30 gives the details of the transducer mounting.
-9 8 - -9 9 -
To vacuum To auxiliary manifold vacuum manifold
To 0 2 To Hg supply bulb manom eter
To oil **“ To product manometer handling system
Transducer BMe3 supply bulb
02 measuring Reaction by lb v_es_se_i _ Temperature bath
Fig. 29. Schematic Diagram of Reaction System for Kinetic Experiments. -100-
To vacuum
inch copper tubing^ A - Electrical connector
Set screw Brass mounting block
- Dewar cover plate
Glass tube
Support
Pressure ®transducer Screw
Brass fitting - Kovar fitting Terminal
Glass to metal seal
Ring seal
To stopcock To stopcock
R eactor
Fig. 30. Transducer Mounting -101-
During the course of this investigation two differ ent reaction vessels were used. Most of the work was carried out in a spherical bulb approximately 8 cm. in diameter; the vessel had a volume of 285.3 oo. and a cal
culated surface of 209.2 sq. cm. giving a surface to volume ratio of 0.73 cm,"\ The other reactor was shaped
in the form of a cylindrical doughnut whose internal
dimensions were 60 mm. for inside diameter, 79.5 mm. for
outer diameter and 10.1 cm. in height; the volume was
24-7.3 cc. and the calculated surface was 4-85.1 sq. cm.
giving a surface to volume ratio of 2.10 cm."^. Con
nections to the cylindrical doughnut reactor were made
at the top of the reactor. The oxygen in let tube was
mounted at a 45° angle to the plane of the top and paral
le l to the plane tangent to the cylinder in order to pro
mote mixing by having the oxygen spiral down the cylinder.
2. The Pressure Transducer 3 The pressure transducer used was an Ultradyne Model
3 J Ultradyne Engineering Labs, Inc., Albuquerque, Hew Mexico.
S-3-RBiID, Serial Ho. 2598 d ifferen tial pressure transducer.
This device consists of two electrical coils mounted in in
dividual chambers which are separated by a metallic dia
phragm; each chamber had a pressure in let port. In
operation a pressure difference between the two chambers -102-
causes movement of the diaphragm and thus changes the relative impedance of the two co ils. With the proper electrical circuit the change can be detected and measured. This particular model can measure pressure differences up to * 1 psi (approx. 50 mm.); however,
in the work reported here, the reference chamber was
kept evacuated and generally used to measure absolute
pressures under 30 mm.
In Figure 31 is the wiring diagram of the elec tr ic a l
circuit used. This circuit was used because the trans
ducer was designed so that the plot of input pressure
against output voltage would be linear when the trans
ducer was operated in an equal impedance ^-arm bridge
circuit. The selection of the bridge load resistance
transformer, transformer connections, and carrier fre
quency were made in accordance with the recommendations
of the man- 'acturer in order to achieve proper impedance matching. Apparently the bridge was not quite properly balanced as the calibration curves show some curvature.
At least a part of the unbalance is in the leads as the shift in the null position exhibited in calibration curves no. 1 and no. 3 (see Appendix E) is the result of revers ing the input leads to the transducer. The circuit was operated with an input of 8.0 volts at a carrier frequency of 20 kilocycles per second provided by the audio o sc illa tor. The output was read on the Heathkit AV-2 Voltmeter I
Heathkit AV - 2 voltmeter
D.RD.T. switch
i M 0 VjJ 1 Pressure Hewlett - Packard ports Model 200 B Audio oscillator ° ~
Terminal Pressure block transducer
UTC LS-33 transformer
Fig. 31. Wiring Diagram for Pressure Transducer Circuit. at a scale setting of 3 .0 = 0.3 volt except for one parti
cular experiment; however, the normal procedure was to use
the meter reading and not the actual voltage. Calibration
of the unit was achieved by measuring the meter reading as
a function of pressure. Pressures for the calibration
were measured using an oil manometer fille d with Dow Corn
ing Silicone Oil 703; conversion of mm. of oil to mm. of
mercury was accomplished with the following equations:
dD.C.703 mmHg * mmD. C. 703 d^
dp q 7Q2 = 1.0900 - 0,00085 t
where dp,q. 703 = density of Dow Corning Silicone Oil 703
dgg = density of mercury at 0°C. = 13.5955 gv./c
t = temperature in degrees Centrigrade
(The equation for the density of the Dow Corning
Silicone Oil 703 was obtained by a least squares treatment
of density measurements obtained from the Dow Corning
Chemical Company in a private communication.)
3. Temperature Measurement and Control
Control of the reaction temperature bath was accom plished in the same manner as described in Section V-B-l-b
4. The Stopwatch
The time measurements made in the kinetic experiment were obtained with a Minerva Model 137 stopwatch. The watch had three hands, two dials and two controls. One -105-
dial was graduated in half minutes and the other in tenths
of a second. In operation both second hands were allowed
to move together; by use of the second control on the watch
one of the hands could be stopped whenever a reading was
desired. After noting the reading, pushing the second
control again allowed the stopped hand to catch up with
the other hand which had kept moving continuously. Use
of this type of stopwatch allowed accurate measurement of
the time at which the reaction pressure was read.
B. Procedure
Because the pressure transducer was rated only for
pressure differentials up to 6 psi without damage to the
diaphragm, it was customary to keep the stopcock open be
tween the reaction vessel and the reference side of the
transducer when the transducer was not in use. After
activating the various electrical systems, the first step
was to close the stopcock between the reference side of
the transducer and the rest of the reaction system; and
then ascertain that the proper vacuum (10**'’ mm.) was
achieved in the reaction system. The pressure in the re
ference side of the transducer was maintained at 10”^ mm.
or lower by continual evacuation by means of an auxilliary vacuum lin e.
1• Measurement of In itia l Oxygen Pressure
Oxygen was introduced into the reactor using the splitting technique mentioned in Section IV-B-2. In a -106- typical experiment values for the pressure of each of the reacting gases were selected and from these the pressure i n i t i a l l y present in the oxygen measuring bulb necessary for introducing the desired amount of oxygen into the re action vessel was estimated. After the desired pressure was obtained in the measuring bulb, it was measured with the aid of the oil manometer. Sometime a fte r the oxygen had been introduced into the reactor (usually toward the end of the reaction), the fin a l pressure in the oxygen measuring bulb was measured and the i n i t i a l oxygen pressure in the reactor was calculated by the following equation:
where PR = in itia l oxygen pressure in the reactor °2 Fn = in itia l oxygen pressure in the measuring bulb 2 P' = fin al oxygen pressure in the measuring bulb °2 ^D.0.703= density of Dow Corning Silicone Oil 703 at the temperature of the manometer
= volume of the reactor
= 285.3 for spherical reactor
= 247.3 for cylindrical doughnut reqctor.
2. Measurement of Initial Trimethylborane Pressure and
Reaction Mixture Pressures
After the in itia l oxygen pressure in the measuring bulb was obtained, the output of the audio oscillator was checked before obtaining the in it ia l trimethylborane -107-
pressure. Assured of the proper operation of the
transducer measuring circuit, trimethylborane was expanded
from the supply bulb (at -80°G.) into the reactor and con
necting line. When the proper pressure was obtained the
reactor was closed off and the excess trimethylborane in
the reactor was condensed back into the supply bulb now
cooled with liquid nitrogen.
(Some reactions were performed in the presence of
added gases. Todbtain the pressure of an added gas the
following procedure was used. After introducing the
trimethylborane in the manner discussed above, the line
adjacent to the reactor was filled with the gas to be
added at a pressure greater than the sum of the trimethyl
borane pressure and desired pressure for the added gas.
By sligh tly opening the stopcock to the reactor, the de
sired amount of gas was allowed to enter the reactor. After
fillin g ,th e excess gas was condensed into a removable bulb
on the submanifold and the meter reading noted. By sub
tracting the initial trimethylborane pressure from the
total, the pressure of the added gas was obtained.)
After the meter reading was recorded for the initial
trimethylborane pressure (and that for any added gas), the
stopcock between the reaction vessel and the oxygen measur
ing bulb was rotated through 180° allowing a portion of the
oxygen to enter the reaction vessel in a short interval of time. At the instant the needle of the voltmeter moved -108-
indicating the entrance of oxygen into the reaction vessel
the stopwatch was started. Then meter reading-time mea
surements were made throughout the course of the reaction.
Because of the speed of the reaction it was customary to
list the meter divisions and half divisions on paper prior
to the reaction; thus when the needle passed one of these
points only the time had to be recorded in its proper
place.
3. Analysis of the Products
The treatment of the products fa lls into three
classes (l) analysis of the products of a single experiment
for unreacted oxygen and trimethylborane and for dimethyl-
borylmethylperoxide formed during the reaction, (2) ac
cumulation of the condensables of several experiments fol
lowed by analysis for dimethylborylmethylperoxide,
(3) special treatment designed to detect minor by-products.
For the analysis of the products of an individual ex
periment the following procedure was used. After the
experiment was completed, the reactor was opened to the
product train, the traps of which were immersed in liquid
nitrogen. Using the Toepler pump the non-condensables
were pumped out and measured. (In some cases the non-
condensables were fin a lly moved into a gas phase chromato graphy sampling bulb for qualitative analysis.) Then the condensable products were fractionated through traps at
“118, —142 and-196°C. (In some of the later experiments -109- an extra fraction was obtained in a trap cooled by a mixture of isoprene and Skelly Solve F to approximately
-155°C. T,his fraction corresponds to the fraction of the explosion limits and usually was very small.) The material collected in the trap at -196°C. was assumed to be unreacted trimethylborane and was measured in the gas burette after transferring it there with the Toepler pump. o The material collected in the traps at -118 and -142 C. was transferred into a sodium iodide test solution (see
Section III-E-4-a) and the amount of peroxide determined by titration of the liberated iodine with approximately
0.01 M sodium th iosu lfate. It was customary to allow the sodium iodide te st solution to stand at room tempera ture for 1 hour after introduction of the peroxide in order that the liberation of iodine would be complete.
After the stopcock was opened on the weighing bulb to ad mit air, the test solution was emptied through the side arm into an Erlenmeyer flask containing 10 cc. of isoprop anol. The bulb was rinsed with three 5 cc. portions of isopropanol which were also added to the test solution in the Erlenmeyer flask . The solution was then titrated with a standard sodium thiosulfate solution until the yellow iodine color just disappeared; during the titra tio n the solution was agitated with Teflon coated magnetic stirrer.
In those cases in which the condensables were accumu lated over a group of experiments, the condensables were -110- fractioned through traps at -80, -142 and -196°C. The fraction collected a t-142 was analyzed for peroxide. The importance of the separation of the peroxide from t r i- methylborane will be discussed in the results.
The special treatment given the products of a few experiments w ill be mentioned in the section on results.
Special treatment requiring detailed description is re ported in Appendix F.
C. Treatment of the Data
In order to obtain in itia l rates and rates at given trimethylborane pressures the following procedure was used. After obtaining the data, a plot of -£p against time was made, and a smooth curve drawn through the points.
Since there were in su fficien t data during the in itia l por tion of the reaction to determine the true shape of the curve in the in it ia l portion of the curve, the curves were drawn such that the in itia l rate was the maximum rate.
(While it may be argued that the presence of an induction period, even though small, is an indication that the rate starts low, increases to a maximum and then undergoes the normal decrease with decreasing concentration, the data indicate that the attainment of such a maximum rate would have to occur quite rapidly. Thus it is very doubtful that a maximum rate could be determined with any more accuracy nor would be any more reliable than the treatment presented here.) - I l l -
After the -Jbp versus time curves were obtained,
rates were obtained at 0.5 mm. intervals by reading the
slope of a line tangent to the curve at the point in
question. After obtaining these rates, graphs were made
of rates versus trimethylborane pressure. (For the ex
periments at -20.0°C. the pressure decrease rather than
the trimethylborane pressure was used.) Smooth curves
were drawn through the points and these curves were used
to obtain both the in itia l rates and the rates during the
course of a single experiment.
D. Results
The data for the individual experiments are given
in Appendix E.
1. Products and Stoichiometry of the Reaction
a) Analysis of dimethylborylmethylperoxide. The re
action of trimethylborane and oxygen at pressures below the
explosion limit yields dimethylborylmethylperoxide as has
been shown by Petry (15). The amount of dimethylboryl-
peroxide formed in the various experiments was determined
by reaction with a sodium iodide test solution (see Section
III-E-4.-a) and titration of the liberated iodine with a
standard sodium thiosulfate solution. The percentage yields
of the peroxide based on the reactant present in lesser
amounts are given in Tables 9 and 10.
In regard to these results there are several factors which may cause the yields to be low. These factors TABLE 9
TOTAL PRESSURE DEGREASE AND PEROXIDE YIELD AT 19.9°C.
Experi p / •. P~ Pe roxide ment ^b (ch3)3 2 " ^ T o ta l Y ield ($)a Remarks Reactor 1 K-l 5.2 6.0 5.4 96 K-2 5.2 5.3 5.2 85 K-3 5.1 10.8 5.0 94 K-4 5.2 9.1 5.1 92 K-5 7.5 6.7 6.7 93 K-6 7.5 6.3 6.3 >68 I.R. obtained B(CH^)^ not separated K-7 7.5 4.0 ^ 4.0 90 K-8-P (6.9)b (7.5 )b (7 .l)° 94 K-9 10.0 5.7 5.7 K-10 7.5 7.3 7.3 K-ll 7.5 8.1 7.7 ^89 K-12 7.5 6.0 6.0 K-13 6.0 5.2 5.2 ) K-14.d 5.2 6.1 5.5 1> K-15d 7.5 6.8 6.8 - 96 K-16 d 5*2 v 4*4 v 4.4 M K-17-P (l0 .0 )b (11.3)? (10.5) '. 98 K-18-P (l0 .0 )b ( l l .4 ) b (10.3 )c K-19 e 5.2 5.2 5.2 • 92 K-20 6 5.3 5.2 5.3 K-33 8.4 4.0 4.0 71 24 hour delay before peroxide determina tion K-36 8.0 3.4 3.4 87 K-37 f 5.0 5.1 5.1 > 89 Mass spectrum obtained K-38 5.9 5.4 5.5 100 K-39 5.0 5.9 5.9 > 92 Mass spectrum obtained
a Based on the reactant present in lesser amount. b Total initial pressure of this and preceding experiment, c Total pressure decrease of this and preceding experiment. d Performed in the presence of carbon dioxide. e Performed in the presence of neopentane. £ Performed in the presence of propylene. -113- TABLE 9 (continued)
Experi Per oxide ment pb (ch3)3 ”^ T otal Yield(^) a Remarks
Reactor 2
K-40 7.5 10.2 7.7 96 K-41 7.5 7.3 7.3 ~) K-42 7.5 5.0 5.0 I-94 Separation of B(CH K-4 3 5.0 5.2 4.9 ( from peroxide pro K-44 5.0 9.3 5.1 J bably incomplete
a Based on the reactant present in lesser amount0 TABLE 10
TOTAL PRESSURE DECREASE AND PEROXIDE YIELD AT-20.0°C
Experi Peroxide ment fb (ch3), po2 -4 pt °t8l Y ield (%) a Remarks Reactor 1 K-21 5.2 excess — 90. K-22 5.1 3.5 3.5 } 70 5 hrs. elapsed befor K-23 5.1 1.8 1.8 J ^peroxide determina K-24 5.1 2.8 3.0 tion K-2 5 5.1 5.1 5 .1 y 75 These reactions K-26 7.-4 5.4 5.5 J possibly not carried K-27 6.6 6.0 6.5 ^ to completion K-28 6.5 11.2 7.7 f 95 K-29 d 5 .i . 8.4 . 6.0 J K-30-P (11.1)b (13. 6 ) a3.3)c 88 After I.R. obtained K-35 9.9 8,1 9.1 > 70 Mass spectra ob tained 3 (0113)3 present
Reactor 2 K-45 6 .4 3.9 4.1 95 K-46 6.5 6.1 6 .4 99 K-47 6.4 7.1 7.3 96 K-48 6 * 5.1 5.4 93
a Based on the reactant present in lesser amount, k Total initial pressure of this and preceding experiment. c Total pressure decrease of this and preceding experiment. ^ Performed in presence of neopentane. -115-
include the following:
(1) The amount of peroxide formed in a single experi
ment is small (0.05 to 0.12 mmoles); thus the results will
be susceptible to minor effects.
(2) Rearrangement and decomposition of the peroxide
at room temperature is known to occur (15); thus small
amounts of peroxide may be lost in transfers. (Loss from
this cause is not lik ely to be very large because of the
slow rate.)
(3) It has been observed that whenever the peroxide
comes in contact with mercury as in a manometer, McLeod
gauge or Toepler pump, there is a scum formed. Since
there is mercury vapor throughout the system, there is
lik ely to be some loss of the peroxide through this
rea ction,
(4 ) As previously mentioned in Section III-E-4-b,
trimethylborane will interfere with the iodometric deter
mination of the peroxide; and therefore, must be separated
from the peroxide before the determination is made.
(5) Mercury also appears to give an interference with the iodometric determination of the peroxide; however,
this interference is not as effective as that from the
trimethylborane.
From consideration of the above factors and the fact that initial pressures have a likely error of 2 per cent, it is not surprising that the yield of peroxide generally -116-
ranges from 90 to 98 per cent. For the experiments per
formed at 19.9°C. there are several values of the peroxide
yield which f a ll below 90 per cent; however, most of these
readily explained. Experiment K-6 is a clear case of
interference from trimethylborane as no separation was
attempted. Some of the other yields are low because of
the failure to achieve complete separation of unreacted
trimethylborane from the peroxide fraction; K -36 is a
lik ely example of th is. The products of K-33 were allowed
to stand for 24- hours before the determination of the
peroxide was made; thus decomposition of the peroxide may
be the cause of the low yield. For several of the experi
ments a mass spectrum of the peroxide fraction was obtained
before making the peroxide determination, and the lo u
yields merely reflect the loss of material in the mass
spectrometer. The cause of the low yield for K-2 is not
known.
Starting with experiment K-3S a slight modification
was made in the peroxide determination. It had been noticed
in earlier experiments that some of the sodium iodide test
solutions had a slight yellow coloration when originally made, but upon degassing of the solutions the coloration
disappeared. This phenomenon was attributed to reaction with mercury condensed in the solution during degassing
operations, and the conclusion checked by adding mercury to a sodium iodide test solution containing iodine -117- liberated by reaction with air. On standing some weeks the solution changed from deep red to a straw yellow color. Since the coloration of the freshly made test solu tions corresponded to only 0.0006 mmoles of peroxide (<.1$ of total peroxide formed during reaction) precautions were taken to prevent contact with mercury during degassing and starting with K-3S all test solutions were used with the coloration present to help counteract the mercury condensed in the solution during the transfer of the peroxide into the solution. A separate experiment showed that the mer cury introduced by cooling with liquid nitrogen and opening the. weighing bulb to the submanifold for a period of time equal to that for a normal transfer was sufficient to de colorize the solution. Since a transfer involves a mass flow of material into the weighing bulb, then more mercury is likely to be introduced during a transfer of peroxide into the weighing bulb because of entrainment. Consider ing the small amount of iodine present originally in the weighing bulb and the probable amount of mercury introduced during a transfer, it is interesting to note that experi ments after K-3S generally have higher yields of peroxide.
b) Stiochiometry. For the reactions performed at
19.9°C., it is noticed that the peroxide yields approach
100 per centj the total pressure decrease is equal to the initial pressure of the reactant present in lesser amount within the limits of experimental error (see Table 9); and -118- the ratios of trimethylborane consumed to oxygen consumed given in Table 11 are approximately 1:1 except for K-36 for which the peroxide determination suggests that the recovery of unreacted trimethylborane was incomplete.
These factors lead to the conclusion that the stoichiometry of the reaction is given by the equation
b(ch3)3 + o2 — » (ch3)2booch3. o The results for experiments performed at -20.1 C. are not in complete accord with this stoichiometry. As shown in Table 10 either the pressure decrease is excessive or the peroxide determination is low. It appears that these experiments for which the pressure decrease gives good agreement with the above equation were actually stopped too soon and thus the low peroxide yields resulted from incomplete reaction. This is likely to be the case since the experiments with the excessive pressure decrease and higher peroxide yields were allowed to react for a longer time. The results in Table 12 indicate that at this tem perature the oxygen consumption is approximately 6 per cent greater than the trimethylborane consumption. For those reactions which appear to be complete, the relative pressure decreases are given in Table 13 and the relative decrease appears to be greater when oxygen is in excess.
Thus i t appears that the excess pressure decrease is caused by an interaction of oxygen on the reaction product, di- methylborylmethylperoxide. If this is the case, the TABLE 11
STOICHIOMETRY OF REACTION BELOW THE LIMIT AT 19.9°C
In itia l Amounts Amounts Recovered Amounts Consumed B(CH3)3 Consumed (mmoles) Experiment „ (mmoles) (mmoles) 02 Consumed b (ch3 )3 o2 b (ch3)3 B(CH3)3 a
K-l 0.081 0.094 — 0.010 (0.081) 0.084 0.96 K-2 0.081 0.083 — 0.001 (0.081) 0.082 0.99 K-3 0.080 0.169 - 0.090 (0.080) 0.079 1.01 K-4 0.081 0.142 0.001 0.064 0.080 0.078 1.03 K-5 0.117 0.105 0.017 0.001 0.100 0.104 0.96 K-7 0.117 0.062 0.056 0.001 0.061 0.062 0.98
K-8-P 0.108 0.117 0.001 0.007 0.108 0.110 0.98 119 K-31® 0.081 0.083 — 0.001 (0.081) 0.082 0.99 K-36 0.125 0.053 0.060 0.001 0.065 0.053 1.23 K-37 d 0.078 0.080 — 0.001 (0.078) 0.079 0.99 K-38 0.092 0.084 0.009 0.001 0.083 0.083 1.00 K-39 d 0.078 0.092 - 0.015 (0.078) 0.077 1.01 K-40 e 0.102 0.138 0.001 0.037 0.102 0.101 1.01
Values in parenthesis are based on total consumption of initial material. b Experiment performed in the presence of neopentane. c This value may be high due to incomplete recovery of the trimethylborane. d Experiment performed in the presence of propylene. e This experiment performed in cylindrical doughnut reactor - a ll others in spherical reactor. TABLE 12
STOICHIOMETRY OF REACTION BELOW THE LIMIT AT -20.1°C
In itia l Amounts Amounts Recovered Amounts Consumed B(CHo), Consumed Experiment (mmoles) (mmoles) (mmoles) ------b (ch^)3 o2 b(ch3 )3 o 2 b(ch3 )3 o2 o2 Consumed
Reactor 2 K-45 0.100 0.061 0.042 0.001 0.053 0.061 0.95 K-46 0.102 0.096 0.014 0.001 0.088 0.095 0.93 -12 K-47 0.100 0.111 0.001 0.005 0.100 0.106 0.94 K-48 0.102 0.080 0.028 0.001 0.074 0.079 0.94 0 -121- compound (s ) resulting from the interaction must have low o vapor pressures at -20.1 C. in order to explain the de crease when trimethylborane is present in excess. In view
of the fact that the peroxide yield was never excessive, a diperoxide of the formula CH^eKOOCH^^ does not seem to be a likely product.
TABLE 13 o o RELATIVE PRESSURE DECREASE OF REACTION AT -20.1 •
Reactant Experi Initial Pressure -4P/P± ment "APTotal of Lesser Reactant in Exces (Pi) Reactor 1 K-27 6.5 6.0 1.08 BMe0 K-28 7.7 6.5 1.18 °2 3 K-29 6.0 5.1 1.18 °o u K-30-P (13 .3 )a ( l l . l ) a (1.2 0 )a ( o |) b K-35 9.1 8.1 1.12 BMe-j Reactor 2 K-45 4.1 3.9 1.05 BMe ^ K-46 6.4 6.1 1.05 BMeo K-47 7.3 6.4 1.14 02 K-48 5.4 5.1 1.06 BMe^
Total for this and preceding experiment. b For overall consideration of the two experiments.
2. Minor Products
a) Non-Condensables. Gas phase chromatography of some of the non-condensables samples collected from kinetic ex periments showed the presence of methane, nitrogen and unreacted oxygen. The nitrogen was present in the origi nal oxygen supply; however, considering the enrichment of nitrogen in the non-condensable fraction caused by removal of oxygen by reaction, the nitrogen content in the oxygen supply was less than 1 per cent. Since the entire series of kinetic experiments was performed with only a single f illin g of the oxygen supply bulb, then the presence of this small amount of nitrogen should have little if any effect on the results. The methane \jas detected in only trace amounts (<.0.0001 mmole).
b) Cg fraction. The separation of the fraction
(02^ , ^2^2 an<^ ^2^ from unreacted trimethylborane, was a problem since trimethylborane will slowly pass through a trap at -14-2°C. In some experiments no separa tion was achieved and the fraction collected was treated as if it were a ll trimethylborane. In view of later re sults, this treatment should not have introduced any appreciable error in the values for the amount of tri methylborane consumed as the amounts of actual Co1s were very small. The first attempts to separate the G ^ fraction from unreacted trimethylborane utilized the tendency of boron compounds to form addition compounds with nitrogen bases. When boron compounds were removed from the reaction mixture by reaction with pyridine, the C2 fraction obtained was found to consist of ethane and carbon dioxide. Hov/ever, the pyridine apparently caused some induced decomposition of the peroxide present (see below) and it is not certain whether the Cg 1 3 which were found arose from the oxidation reaction or results from the action of the pyridine on the products. -123-
In later experiments the C£'s were separated from the unreacted trimethylborane by using an isoprene-Skelly
Solve F slush mixture (temperature approximately -155°C.) to trap the trimethylborane while allowing the C£'s to pass through the trap. The amounts of C 2 ’s collected were very small (<£.0.0001 mmole); however, the gas phase chromatogram of the C 2 fraction from the accumulated pro ducts of four experiments did show the presence of ethane.
c) Other. From several special experiments (see
Appendix F) small amounts (l to 2 percent of in it ia l tr i- methylborane) of other compounds were observed. Methoxy- dimethylborane was observed in the vapor above the pyridine adduct of the products of K-31 (l9.9°C. with neopentane added), in the residue of K-35 (-20.1°C.) and in the G^ fraction of K-39 (19.9°C. with propylene added). In view
of the facts that the decomposition of dimethylborylmethyl- peroxide (15) yields much more dimethoxymethylborane than methoxydimethylborane and that dimethoxymethylborane forms no addition compound with pyridine ( 15 ) and thus should have been detected in the pyridine experiments, it appears that the methoxydimethylborane observed must have been a minor product of the oxidation of trimethylborane.
Although several mass spectra (residue of K-35 and
^4. fraction of K-39) have been interpreted (see Appendix F) as having dimethoxymethylborane present, these interpre tations are not too reliable in that several other -124- components were believed present and the mass spectra of dimethoxymethylborane and dimethylborylmethylperoxide are
somewhat similar. Even if the dimethoxymethylborane is present, it may have arisen from the rearrangement of di me thylborylmethylperoxide rather than directly from the
oxidation reaction.
Although the interpretation that the mass spectrum
of the residue of K-35 contained hydroxydimethyIborane is
somewhat questionable, there is no doubt to the observa
tion th at the spectrum of the vapor above the pyridine
adduct of the products of K-34 (-20,1°C.) indicated the
presence of hydroxydimethylborane. The belief that the
carbonyl band (^5.8 microns) in this same spectrum is formaldehyde suggests that the hydroxydimethylborane may have been formed in the following manner: < T > h 3G qJ o-g-h .S. HrN + (CH,)oB0H + HoC0. H ,C ' * NC H _ 55 3 5 5 5
The mass spectrum of the residue of K-35 has been interpreted (see Appendix F) as having dimethoxymethyl borane, hydroxydimethylborane, methoxydimethylborane and some unidentified species present. Since most of this m aterial should have been i n i t i a l l y removed and th eir presence would not explain the excessive pressure decrease at -20.1°C., it seems likely that in this case these com pounds are lik ely to be due to decomposition of some -1 2 5 - unidentified m aterial which was o rig in ally formed during o the reaction at -20.1 G.
Landers and Volman (4.3) have shown th at methyl ra d i cals from the decomposition of di-tert-butylperoxide induce polymerization of propylene in the temperature range 13 0 ° to 165°C. Petry (15) has shown that in the decomposition of dimethylborylmethylperoxide at 4-7.&°C., the presence of propylene reduced the yields of methane and ethane and also causes the appearance of C hydrocarbons, thus de- 4- monstrating the presence of methyl radicals during the decomposition. An attem pt (see Appendix F) was made to utilize this property of propylene to test for methyl radicals in the oxidation of trimethylborane. Unfortunate ly the small yield of the fraction in which the hydro carbons should have appeared, if present, was too small for an accurate determination of the presence or absence of hydrocarbons, and thus the test was inconclusive.
3. Kinetics
a) Typical curves and initial rates. A typical plot of -Ap against time is shown in Figure 32. In general the curves were smooth with very l i t t l e sc a tte r; however, a few reactions did show a greater degree of scatter than that illustrated in Figure 32. Most curves had an induc tion period of approximately 3 seconds except those in reactor 2 in which the reactions had induction periods of 1 second or less. In the example noted the first point 7
K-IO -12 A p (mm.)
6 -
Q5 0 20 406080 100 120 140 160 180 time (sec.)
Fig. 32. Typical - A p - T im e Curve. -127- corresponds to a slight pressure increase rather than a
pressure decrease. This occurred only occasionally; and
since it was always small, it was attributed to experi
mental error.
In Figure 33 there are two examples of the rate
curves obtained in the manner described in Section VI-C.
The curve for experiment K-10 is typical of many of the
experiments at both 19.9 and -20.1°C. Reactions in which
the trimethylborane pressure was approximately twice the
oxygen pressure gave curves sim ilar to that for K-9
(Fig. 33). In some cases straight lines were obtained.
This also occurred for some of the experiments with added
gases or products present.
In Tables 14- and 15 are given the initial rates for
the reactio n of trimethylborane and oxygen in the absence
of added gases. Included in the tables is a column giving
the value of (-dp/dt) This is the expression
for which a constant was obtained at lower pressures (4-).
As seen from the tables a constant is not obtained for the
pressures studied here.
b) Order of the reaction. In Figure 34- the logarithm
of the initial ra'tes has been plotted against the logarithm
of the i n i t i a l oxygen pressure fo r two d ifferen t i n i t i a l trimethylborane pressures. The slope of this type of curve should give the order with respect to oxygen. From the graph it is seen that the order with respect to oxygen -128-
0 . 2 4
0.20 K-IQ
0.16
K -9 0.12 -dp dt
0 .0 8
0 .0 4
0 2 4 6 8 10 p BMe3
Fig 33. Typical Rate — Trimethylborane Curves. - 129- TABLE 14
INITIAL RATES FOR REACTION AT 19.9°C
Initial Pressures (-dp/dt^ x 10^ Experi- b (ch3)3 o2 (-d p /d t^ p2 p ment (mm.) (mm.) (mm./sec.) r02 BMe3 (l/mm? sec.) Reactor 1 K-2 5.2 5.3 0.102 7.0 K-l 5.2 6.0 0.119 6.4 K-4 5.2 9.1 0.242 5.6 K-3 5.1 10.8 0.280® 4.7
K-13 6.0 5.2 0.104 6.4 K-38 5.9 5.4 0.107 6.2
K-8 6.9 2.2 0.037 11.1
K-7 7.5 4.0 0.070 5.8 K-12 7.5 6.0 0.167 6.2 K-6 7.5 6.3 0.164 5.5 K-5 7.5 6.7 0.181 5.4 K-10 7.5 7.3 0.229 5.7 K-ll 7.5 8.1 0.275 5.6
K-36 8.0 3.4 0.060 6.5 K-3 3 8.4 4.0 0.067 5.0
K-l 7 10.0 5.5 0.144 4.8 K-9 10.0 5.7 0.152 4.7 K-18 10.0 6.0 0.182 5.1
K-32 15.0 4*4 0.127 4.4 Reactor 2 K-43 5.0 5.2 0.103 7.6 K-44 5.0 9.3 0.297 6.9
K-42 7.5 5.0 0.110 5.8 K-41 7.5 7.3 0.455 s 8.8 K-40 7.5 10.2 0.577 7.4
a These values somewhat uncertain because of irregularity in rate -pressure curves, -130- TABLE 15
INITIAL RATES FOR REACTION AT -20.1°C
Initial Pressures (-dp/dt). X 10^ Experi- 02 (-dp/dt)i 6 ------ment (ram.) (mm.) / / \ p0o BMe, (mm./sec. ) 2 3 (l/mm^sec.) Reactor 1 K-24 5.1 2.8 0.031 7.8 K-22 5.1 3.5 0,057 9.2 K-25 5.1 5.1 0.108 8.1
K-27 6,6 6.0 0.148 6.2 K-34 6.7 7.0 0.242 7.4 K-28 6.5 11.2 0.720 8.8
K-26 7.4 5.4 0.151 7.0
K-35 9.9 8.1 0.615 9.5
K-30 11.1 7.3 0.360 6.1 Reac tor 2 K-4 5 6.4 3.9 0.077 7.9 K-48 6.5 5.1 0.158 9.3 K-46 6.4 6.1 0.180 7.6 K-47 6,5 7.1 0,325 0/• 07 -131-
1.40
1.30
1.20 slope ■ 1.6
3 N .10 cr
CO 1.00
slope = 1.9 0.90
0.80 0.5 0.6 0.7 0.8 0.9 1.0
'°q (po2 )i
Fig. 34. Determination of Oxygen Order for Reaction at I9.9°C. in a Spherical Reactor. -132- apparently lies between 1.5 and 2.0 and that it is de pendent on the trimethylborane pressure. k similar plot is shown in Figure 35 from which it is seen that the order with respect to trimethylborane apparently lie s between
0.5 and 1.0 depending on the oxygen pressure.
If one chooses an experiment in which the in itia l pressure of trimethylborane and oxygen are equal, then since the stoichiometry requires equal consumption of each reactant, the pressure of one component will equal the other during the course of the reaction. Thus for these cases, the rate expression should be expressible with one variable providing the products do not enter into the reaction. Two reactions for which the above condition is approximately fulfilled are K-2 and K-10.
In Figure 36, log (-dp/dt) has been plotted against Pbm&3*
For K-2 the overall apparent order is 2.1 and for K-10 it is 2.0. In both cases the order appears to f a l l of as the reaction progresses. This change in reaction order as the reaction proceeds can be attributed to one of three possibilities - (l) an effect due to the actual inequality of the oxygen and trimethylborane pressures, (2) an effect due to the influence of products on the reaction, and (3) an effect arising from the general complexity of the re action. In view of the fact that for K-10 the in itia l t r i methylborane pressure was actually sligh tly higher than the oxygen pressure, the abrupt change near the end of the -133-
id^e * 0.7
slope « 0.5 o» o
+
5.4 6.0
0.9 0.6 0.7 0.8 0.9 1.0
lo<3 ( p BMe3 )j
Fig. 35. Determination of Trimethylborane Order for Reaction at I9.9°C. in a Spherical Reactor. -134-
K—10 lope = £ 0
lope = 2.1
K- 2 0.8
0 6
(V)
0.2
0 0.2 0.4 0.6 08 1.0
l09 p8Me3
Fig. 36. Determination of Overall Order for 1=1 Mixtures of Oxygen and Trimethylborane at I9.9°C. in a Spherical Reactor. -135-
reaction is likely to be an example of (l); but since
this is in the opposite direction of the general trend,
(l) does not appear to be the solution for the general
deviation. On the basis of results to be mentioned
later, (2) remains a lik ely p o ssib ility . The effect cannot
be an example of a pseudo n-order reaction since this type
of reaction increases in order as the pressure is lowered.
If the rate expression consisted of a number of terms of
different order, then the lower order terms might pre
dominate as the pressure decreases. However, the devia
tion from the in it ia l slope cannot be a simple matter of
lowering the pressure, as Bamford and Newitt (4-) have
shown that the reaction at low pressures obeys the ex
pression - ^2 = kPn.. P~ which has an overall order dt BMe3 2 of 3. Thus i t would appear that the complexity of the
reaction at these higher pressures had decreased the
order to approximately 2 and that during the course of
the reaction, the order appears to decrease because of
a catalytic effect of the products.
The results of these data concerning the order of
the reaction suggest that, excluding the catalytic effect
of the products, the rate expression is of the general form suggested by Bamford and Newitt (4.), but shows a retardation: - = dt I
-136-
Thus the order with respect to oxygen would be near 2 if
b is greater than c; also the order with respect to oxy
gen shoudl approach 2 as the pressure of trimethylborane
is increased. This restriction that b is greater than c
is in accord with the apparent order with respect to tr i-
methylborane being near 0.5 and increasing with increasing
oxygen pressure. The overall apparent order might be ex
pected to be near 2.0 if the co efficien t a has the proper
value.
c) Apparent activation energy. The activation energy
is usually defined by the equation
k - I.' E/ET
where k is the specific rate constant at temperature T, A
is a temperature independent constant, E is the gas con
stant and E is the activation energy. If the specific
rate constant is known for two different temperatures
then the activation energy can be calculated from the
equation * _ 2.303R(log kq - log k2)
" I - i t 2 Tq Since the constant A does not appear in this equation
then values directly proportional to lc can be substituted
for k. If one chooses two experiments at different tem
peratures but with identical initial concentrations, then
the rates (expressed in concentration units) may be sub
stituted for the specific rate constants. In Table 16 -137- the results are shown for two sets of experiments to which this treatment was applied. From the values of the acti vation energy obtained it appears that the apparent activation energy is near zero, and the reaction cannot be slowed down by lowering the temperature.
TABLE 16
APPARENT ACTIVATION ENERGY
Experir T (PBMe o ) . x 100 (p02 ^i x 100 (“f f h x 100 ^act. (°K) 5 l dt i ment T T T kcal. (mra/°K) (mm/°K) (mm/sec. °K)
K-5 293 25.6 22.9 0.618 K-27 253 26.1 23.7 0.585 0.4
K—11 293 25.6 27.6 0.938 K-34 253 26.5 27.7 0.956 -0.2
d) Effect of added gases on the rate of the reaction.
The initial rates for the experiments with added gases are shown in Table 17. From comparison of these in itia l rates with those given previously for reaction in the absence of added gases, it is seen that the addition of gases appears to slow doxrn the rate of reaction. Carbon dioxide has a rather small effect, but neopentane and propane reduce the rate by approximately 20 to 30 per cent. Since the reduction does not appear to be proportional to the amount of added gas, it appears that th is is probably a diffusion effect rather than a third-body effect. Unfortunately, a reaction in the absence of added gas was not performed at the trimethylborane and oxygen pressures similar to those -138-
of K- 2 9 ; thus it is not certain what effect temperature
ha s on this ad ded ga s effect.
TABLE 17
INITIAL RATES OF REACTION'S WITH ADDED GAS
Exper i- Initia 1 Pres sures (- dp\ ment \ d t/1 pBMeo PA A (mm. } P°2 (mm. ) (mm. ) (mm./sec. )
19.9°G. K-14 5.2 6.1 4.8 CO- 0.115 K-15 7.5 6.8 5.4 CO- 0.181 K-16 5.2 4*4 10.0 C02 0.066
K-19 5.2 5.2 4.8 c (ch3)/ 0.078 K-31 5.2 5.3 8.8 C(CH ), (°.065)£ax K-20 5.3 5.2 10.0 C(C h 33) 2 0.071
K-37 5.0 5.1 10.0 ch3ch=ch2 0.061 K-39 5.0 5.9 31.3 GH3CH=CH2 0.086 -20,1 C. K-29 5.1 8.4 8.8 c (ch3)4 0.160
n This ex pe rime nt gave an o dd result; a f ter an in ducti on period of 6 seconds, the -&P versus time plot gave vi rtually a str aight line over the next 60 seconds then curved sharply.
e ) Effect of the product on the rate of the reaction.
In Table 18 the init ial rates of e pxeriments per formed in the pre sence o f products are lis ted. Also 1 iste d are the in it i al rates of some comparison experiments whi ch were performed with no pr oducts present initially . Comparison
of the in itia l rates for experiments with added products shows that the presence of products increases the rate.
The surprising part of this increase is that the rate with products added is almost the same as that obtained when -139- trimethylborane is substituted for the products as shown by the comparison experiments. For the -20.1°C. case a suitable experiment had not been performed, but one with the appropriate oxygen pressure is listed. It appears that at -20.1°C. the catalytic effect is not as great; however, these experiments are uncertain because of the excessive pressure decreases encountered.
TABLE 18
INITIAL RATES FOR REACTION IN THE PRESENCE OF PRODUCTS
Experiment In itia l Pressures (-dp/dt)1 ^BMe^ ^Products (mm.) (mm.) (mm.) (mm./sec.)
19.9°C. K-8-P 4.7 5.3 2.2 0.108 K-17-P 4.5 5.8 5.5 0.180 K-18-P 4.0 5.4 6.0 0.133 - 20. 1°c. K-30-P (3.7)a 6.3 (7.3)a 0.123
Comparison Experiments 19.90C. K-13 6.0 5.2 0.104 K-18 10.0 6.0 0.182 K-17 10.0 5.5 0.144 -20.1°C. K-27 6.6 6.0 0.148
o 0 These values based on stoichiometry found at 19.9 C. Since the pressure decrease at -20.1°C. deviates from this stoichiometry, the values are rather uncertain.
If this catlytic effect arises from the dimethyl- borylmethylperoxide rather than some minor product, then it appears that at least for the initial rate, the rate -140-
expression cannot distinguish between trimethylborane and
dimethylborylmethylperoxide. This seems odd in view of
the fact that there is no evidence for the formation of
other products in these experiments. Thus there is no
consumption of peroxide and therefore the effect is one
of catalysis.
f) Effect of surface on the rate of reaction. In
cluded in Tables 14- and 15 are the in itia l rates for
reaction in both a spherical reactor (Reactor l) and a
cylindrical doughnut reactor (Reactor 2). The ratio of
the surface to volume ratios for these two reactors was
approximately 1:3. Comparison of the initial rates for
approximately the same initial pressures in the two
different vessels shows that there is an increase in the
rate, but not anywhere near a threefold increase. also
it appears that the increase in rate is greater for the
reactions with higher oxygen pressures and for the lowest
oxygen pressures the increase is almost non-existent.
Another characteristic of the reactions in the cylindrical
doughnut reactor is that they have shorter induction periods than those in the spherical vessel. This effect
is rather small due to the fact that the induction periods
in the spherical vessel have a magnitude of about 3 sec
onds. Nevertheless, the implication of the shorter induction periods in the cylindrical doughnut reactor is -1 4 1 -
that the surface effect probably involves the initiation
of chain carriers rather than being a contribution from
a reaction occurring wholly on the surface.
g) Interpretation of individual experiments. k s
mentioned in Section VI-D-3-b the reaction appears to be
second order with respect to oxygen and fir s t order with
respect to trimethylborane, but shows a retardation by
each of the reactants:
_ap . k FBMe3 f °2 dt a + bPBMe3 + cP02
This equation neglects any catalytic effect of the pro
ducts. For an individual experiment one may make the
following substitution
PBMe3 = P0o + (PBMe3 ^i “ ^ O ^ i = P02 + e where e = (pBMe3)i - (P02 )i'
Upon rearrangement of the f ir s t equation and substitution
of the second, one obtains the following:
?BM93 Pq2 = _a_ + be + /b + c\ p -dp/dt k k ... \ k J °2
Thus a plot of vs. -dp/dt should yield a straight
line of slope ^-b j and an intercept of the value
Plots of th is type are given in Figures 37, 38,
39 and 40 and the initial pressures for the experiments illu strated are summarized in Table 19. The values of -142-
2.0
K- 10 * " n a (U K- 7 (/> K -12 (VI e E
O
x
0.8 cvj O ro Q> 2 CD 04
0 2 4 6 8
p0 2 (mm •)
Fig. 37. Test of the Retarding Effect of the Reactants. - H 3 -
2.0
d 8 K—12 >0=0 E E
O
X
csj cm O Q. ro 0)
LL 0.4
0 2 4 6 8
Pq 2 (mm.) + C
Fig. 38. T est of the Retarding Effect of the Reoctants.
/ - 1 U -
2.4
K- 20 2.0
K-10
a.
(M CM 0.8 IO
0.4
0 2 4 6 8
Pq 2 (mm.)
Fig. 39. T est of the Retarding Effect of the Reactants. - H 5 -
2.0
K -10 K - 27
K -41 ^ 0.8 K>
0.4
Fig. 40. T est of the Retarding Effects of the Reactants. TABLE 19
REFERENCE TABLE OF FIGURES 37, 38, 39 AND 4.0
Initial Pressures P P Intercept Slope Experiment rBMe3 02 (mm.) (mm.) (mm.“sec.) (mm.sec.)
Figure 37
K-7 7.5 4.0 -0.19 0.477 K-12 7.5 6.0 0.14 0.247 K-10 7.5 7.3 -0.06 0.245 K-ll 7.5 8.1 -0.24 0.247
Figure 38
K-l 5.2 6.0 0.06 0.2 52 K-12 7.5 6.0 0.14 0.247 K-18 10.0 6.0 0.08 0.293 K-17-P 4.5 5.8 -0.31 0.200
Figure 39
K-2 5.2 5.3 0.14 0.244 K-10 7.5 7.3 -0.06 0.245 K-20 8 5.3 5.2 -1.65 0.702 K-32 15.0 4.4 -0.42 0.612
Figure 40
K-10 7.5 7- 3 >, -0.06 0.245 K-4.1 7.5 7.3 b -0.10 0.133 K-2 7 6.6 6.0 c 0.32 0.216
8 Performed in the presence of 10 mm. of neopentane. b Performed in Reactor 2. c Performed at -20.1^0. -147-
the trimethylborane and oxygen pressures throughout an
individual reaction were based on the initial pressures
and the stoichiometry given in Section VI-D-l-b (i.e.,
one mole of trimethylborane reacts with one mole of oxy
gen to give one mole of products). The rate data were
obtained from rate-trimethylborane pressure curves.
From the various graphs it can be seen that for the
initial stages (i.e., higher pressures) all reactions yield a straight line; however, many of them show
deviation during the latter portion of the reaction.
Although the latter portion is subjected to the greatest
error and therefore somewhat uncertain, these deviations
may be real. In fact deviation below the initial straight
line is to be expected if the product catalyzes the reac
tion. The deviations above the line are probably due to
a diffusion effect involving the gas in excess. However,
the deviation encountered in K-27 (Fig. 4.0) may involve
some temperature effect rather than a diffusion effect.
The reactions plotted may be divided into three
classes with regard to their slopes. These three classes are (l) those with slopes the same as K-10, (2) those with slopes greater than K-10 and (3) those with slopes less than K-10. In Figure 37 are plotted four reactions with the same initial trimethylborane pressure. Three of these reactions appear to fall in class 1 and one in class 2.
It is noted that K-7 (class 2 example) has an in itia l -148- trimethylborane pressure which is almost twice that of the in it ia l oxygen pressure. In Figure 38 are reactions which virtually have the same in it ia l oxygen pressure.
(Note: Some of the experiments in this figure have been shifted on the oxygen axis in order to separate the points 5 therefore, care should be used in comparing the experiments.) For these curves two are class 1, one is class 2 (again a high ratio of trimethylborane to oxygen), and one a class 3. The class 3 example is one for which products were in itia lly added. The much lower position of this experiment on the graph is probably reflective of the catalytic behavior of the product. In Figure 39 there are two reactions of class 2 , one with a large excess of trimethylborane (K-32 ) and one with neopentane added (K-20). The other two reactions in the figure are class 1 examples. Since K-2 and K-10 have nearly the same trimethylborane to oxygen ratio but different initial pressures, these reactions indicate that the class 1 de signation is not particularly sensitive to total pressure at a given mole fraction of oxygen.
The experiments given in Figure 40 have nearly the same initial concentrations of trimethylborane and oxygen.
The reaction K-41 was performed in reactor 2 and the change in slope is probably due to increased initiation of chain carriers caused by the increase in the surface. Reaction
K-27 was performed at -20.1°C. The pressure of reactants -149- of this experiment were obtained from the rate -^p curve Ad and the assumption that PgMe^ = ^ °2 ^ ^Pt* ^ us data for this experiment are somewhat uncertain; however, it appears that the catalytic effect of the products is reduced at this temperature. On these same graphs the intercept should be given by (— ~~~—) . Since e is positive when trimethylborane is in excess and negative when oxygen is in excess then one could expect the inter cept to be positive or negative depending on whether t r i methylborane or oxygen was in excess. For the experiments this appears to be the case except K-10 has a slight negative intercept when it should be positive. However, those experiments of class 2 are greatly displaced to the negative direction. This is difficult to explain. About the only way to introduce a negative term into the denomin ator of the rate expression is to include a branching term.
This does not seem likely since branching would most likely introduce side products and it is difficult to see how an added gas such as neopentane could aid branching. Of the two examples of class 3, K-17-P should have a negative intercept; however, K-41 should not. The true s ig n if i cance of these deviations in the intercept is obscure.
In general the straight lines obtained in the plots 2 of PBM P(V/(-dp/dt) against P0 indicate that the rate B 2 u2 expression is approximately valid. Since the slopes are -150-
not a ll equal, it appears that c is not actually
a constant. Since the reaction appears to be a chain
process that begins on the walls, the terra k in the rate
expression should include a specific rate constant for the
in itia tio n step. Thus any changes in the reaction condi
tions which affect the apparent value of the rate constant
for the initiation will change the slope of the line ob
tained in the above plots. Thus large excesses of tri
methylborane or the presence of added gases should impede
the transfer of oxygen to the wall; therefore, if oxygen
is involved in the initiation step, then the apparent
value of k should be smaller than it normally is. This
results then in an increased value of the slope of the
lines as seen in the graphs.
The experiments of class 3 are also consistent with
the idea that k is affected, For the case of the reaction
in reactor 2, the increase in surface area should cause k
to be larger, thus resulting in a smaller value of v.'lT/
The effect of product catalysis may also be interpreted
as involving the initiation process. In fact an increase
in initiation by products, is one way the products could
cause a large increase in rate without producing a corres
ponding amount of side products. Here too, one would expect a higher value of k resulting in the observed lower values -151-
h) Comparison of initial rates with rate expression.
In view of the agreement of the individual experiments with the rate expression, it is disappointing to notice that the initial rates do not give as good agreement. If the rate expression is valid, then for those experiments with the same trimethylborane pressure the values of
(-dp/dt L/ p£ P given in Tables 14 and 15 should de- 2 crease with increasing oxygen pressure. For the series K-l through K-4 this is true; the series K-5 through K-12 is indecisive as is the narrow series of K-9, K-17 and K-18.
This indecisiveness may be due to scatter caused by variation in the mixing of the gases. Such an effect should be more important at the higher pressures. It is interesting that as the trimethylborane pressure is in creased in each of the above series the average value of
(-dp/dt^Q PBMe^ ^oes decrease as would be expected from the rate expression.
For the reactions at -20.1°C. the series K-22, K-24 and K-25 is indecisive; again this may be due to scatter.
However, the series K-27, K-28 and K-34 requires a negative value of c if the rate expression is to be valid. Whether this is a result of scatter or not is not certain, but in view of the other complications observed at this temperature, it is likely that there is some modification of the reaction mechanism at this temperature. VII. DISCUSSION
A. Mechanism of the Reaction Below the Explosion
Limit
In general the reactivity of boron compounds toward oxygen and nucleophilic reagents can be attrib u ted to the tendency for coordination between the reagent and the open sextet of the boron. Johnson and Van Campen have reported
(12) that the ease of cleavage of a boron-alkyl linkage by reaction with hydrogen bromide, bromine, perbenzoic acid, hydrogen peroxide and oxygen forms the series R^I^RgBX^
RBX2 where X = halide, hydroxyl or alkoxy group. The re a c tiv ity toward oxygen has been shown to follow the series (C H ^ B ^ H ^ B (CH=CH2 )2>(CH2=CH)3B. The re a c tiv ity of tr iv in y l- and methyldivinylborane toward oxygen was demonstrated by Parsons, Silverman and Ritter (4-4) who mixed each of these gases with an excess of dry air
(to tal pressure 200 mm.) at 25°C. On standing two hours in the gas phase the trivinylborane-air mixture underwent no reaction, but the methyldivinylborane was 70 per cent consumed in ninety minutes. These correlations between re a c tiv ity and the Lewis acid strength of the boron com pounds indicate th a t coordination of a donor with the open sextet of the boron is involved in these reactions.
In view of the observations here and those reported by Petry (15) that the reaction of trimethylborane and
-152- -153- oxygen below the explosion lim it yields dimethylboryl- methylperoxide in essentially quantitative amounts, the reaction could be explained in terms of a coordination of an oxygen molecule with the open sextet of the boron followed by a migration of the methyl group:
C H o* 0: «JT\ (CH3)3B + 02 — > CH3- 3:0: (CH3)2B00CH3 i CH3 J However, this mechanism should yield second order kinetics instead of the complex rate expression obtained in this study or the third order kinetics obtained by Bamford and
Newitt (4 ) at low pressures. In addition to the failure to agree with observed k in etics, the above mechanism is rather doubtful from theoretical considerations. In the ground state the oxygen molecule has two unpaired elec trons and the formation of the above complex would involve the pairing of these electrons - a process which is likely to have high energy requirements. Furthermore, the forma tion of the addition complex would require a tra n s itio n of the bonding on the boron from sp hydrides to sp-5 hybrides which also would require energy. Also boron t r i methyl is stabilised by "trigonal hyperconjugation" by an amount estimated by a semi-empirical molecular orbital computation to be 1.5 to 2 electron volts (45). Thus it seems unlikely that the energy obtained from bond forma tion would be sufficient to off set the energy -154- requirements involved.
The formation of a one electron coordination bond would have much lower energy requirements since the pairing of
the unpaired electrons of the oxygen molecule would no
longer be involved; however, less energy would be obtained from such a bond and it is unknown if such a coordination bond would be stable.
I From the observed kinetic data, restrictions to the actual mechanism can be readily obtained. The complexity
of the rate expression suggests that the reaction proceeds by a chain mechanism - a conclusion supported by inhib itio n by mixtures of trifluoroborane and water ( 4 ). The existance of an explosion region is also suggestive of a chain mechanism. Secondly it would appear that these chains start on the walls. This is supported by the in duction period, the rather mild surface effect, the effect
of added gases on the rate and the observation that a large excess of oxygen in experiments where trimethylborane is admitted to the reactio n vessel containing oxygen causes a reduction in the rate ( 4 ). The lack of a d e fin ite sur face effect at low pressures of oxygen in the cylindrical doughnut reactor indicates that the chains probably ter minate on the wall, and thus an actual increase in initiation is probably counter-balanced by a shortening of the chains. (In the cylindrical doughnut reactor, the nearest wall is always within 5 mm., but in the spherical -1 5 5 - reactor the maximum distance to the wall is 1+0 mm. - the radius of the bulb). k t higher oxygen pressures the
small increase in rate in the doughnut reactor is probably due to the fact that the turbulence caused by admission of
the oxygen is su ffic ie n t to upset the balance of the in creased initiation and shorter chains. Since the inlet tube of the oxygen was designed so as to allow the incoming
oxygen to sp ira l down the cylinder, then at higher oxygen pressures the rate of tran sfer of oxygen to the walls
should be greater - thus causing an increase in initiation above normal. Therefore, from consideration of the kin etic data, the reaction is expected to proceed by a chain reaction that begins and ends on the walls.
In view of the fact that the reaction yields dimethyl- borylmethylperoxide and only trace amounts of other products the chain mechanisms must be re la tiv e ly simple. With con sideration of the above conclusions, the following general mechanism is proposed fo r the reaction below the lim it:
1) BMe^ + wall + 02 — X
2) X + 02 y 1c ^ 3) X + BMe^ * X + product k/ 4.) X + wall —-^termination
5) X + wall — ‘^termination.
In regard to reaction 1 it is assumed that the trimethyl
borane is strongly adsorbed on the wall and thus, the concentration of the adsorbed trimethylborane is constant -156
and the rate of reaction 1 is independent of the tri-
methylborane pressure. No restriction is made on whether
the oxygen is on the surface or in the gas phase as oxy
gen would most lik ely be weakly absorbed and thus the
concentration of oxygen on the walls would be proportional
to the oxygen pressure.
Assuming a steady state condition for the chain
carriers X and J, the following is obtained.
a g l e t = jo .;] -k 2 [ y ] [ o 2] k k3 0 ] [b m s3] - k 2 [ x ] = 0 (I)
(i d
By adding equations I and II it is possible to solve for
0 0 in terms of £x]and the known concentrations.
[Y] . *1 f°a3 - h . (I ll)
The solution of £xj may now be obtained by substitution
of equation III into II#
(IV)
Substitution of IV into III gives a solution for [ i j .
kl k2 [0 2] 2 (V) Cl] = k4k5 + jjBMe^ + k2k5 £°21
Solving for the rate of disappearance of trimethylborane and oxygen equation VI and VII are obtained. - 1 5 7 -
kl k2k3 fBMe3] M (VI) = k. dt k4k5 + k3k4 [BMe3] + k2k 5 [°2 l
~d [0J _ k f 0 -t + k l k 2 k 3 [3a e 3^ 02^2 + W s E a f (y II) At 1 2j + k4k5 ♦ kjk^ [BHe^ + k2k5 i02J
Since Bamford and Newitt (4) from consideration of
the inhibition of the reaction by mixtures of trifluoro-
borane and water at lower pressures obtained a minimum
average chain length of 50, then the consumption of
reactants by initiation is small and the k-j_ C ° 2 l term
may be neglected in equations VI and VII. From these
equations it would appear that the rate of disappearance
of oxygen would be greater than the rate of disappear
ance of trim ethylborane. In view of the stoichiometry
of the reaction this does not seem possible. This diffi
culty can be overcome if one considers the numerator of the second term of equation VII. The first term of this numerator corresponds to a long chain reaction, but the second term corresponds to a very short chain consisting of reactions 1, 2 and 5. The latter process would produce only the product of reaction 5. Since the reaction produces dimethylborylmethylperoxide in essentially quantitative yield and long chains have been observed, then k^ and most likely the predominate chain ending step is reaction 4. This restriction yields -158- further agreement with the observed results. Reactions
2 and 3 are both propagation steps and probably have velocity constants of the same order of magnitude. Thus, if k^^k^., then k^k^ ^ k^k^ ^ k^k^ which agrees with the observed rate expression in that b> c > a .
Therefore, by employing the restrictions mentioned above which were based on experimental observation, we arrive at the rate expression
-d|BMe£j -dJjD^J -a {dpj k^k2k^ ^BMe-J {O2I
dt dt dt + k3k4 CBMe3] + k2k5 C°2^
(VIII) where p is the pressure and a is a proportionality con stant.
By comparison with the observed rate expression
-dpZ. = ______kPBMeoP0o3 2 ______f •+ it • is seen that , k = dt a + bPBMe^ + cP^ O a k^k2k^j a = k 4,^5 5 b = ak^k^ and c = 0^ 2^..
Since the wall termination reactions 4- and 5 are lik e ly to have small activation energies, the near zero value for the apparent activation energy implies that the activation energies for reactions 1, 2 and 3 are small.
In attempting to specify the chemical nature of the chain carriers, emphasis is placed on the propagation reactions 2 and 3. Petry (15) has suggested that the chain carriers may be 2 = CH^* and Y = CH^OO*. In this -159- scheme reaction 3 is visualized as a radical displacement reaction in which the activated complex probably involves a coordination complex between the methylperoxyl radical and trimethylborane. (bote: Unlike the oxygen molecule, ailcylperoxyl radicals have an unshared pair of electrons in a p orbital on oxygen and therefore, should have a greater tendency to form coordination bonds.) However, reaction 2 would be CV - °2— >°vy and th is reaction has been shown to be a third order re action involving a third body to remove excess energy for stabilization of the methylperoxy radical ( 46). Since the addition of neopentane suppresses the reaction in stead of enhancing it , this reaction seems very unlikely.
It is conceivable that there is a third body effect which is masked by the effect which suppresses the rate, but this would require that the suppression effect have a larger magnitude than seems reasonable. Thus it does not appear that GH • and CH„0o * are the chain carriers. 3 ^ 2 Another set of chain carriers would be and (GH^^BOO*. In this case reaction 2 would not necess arily require a third body as the peroxyl radical probably has sufficient vibrational modes to be stabilized. Reac tion 3 now becomes
(gh 3)2boo - + (ch3)3b ------> (ch3 )2booch 3 + (ch3 )2b - and presumably, would involve an activated state in which - 1 6 0 - one of the oxygens of the peroxy radical coordinates with the boron atom in trimethylborane. (The use of the open sextet on the boron during the formation of the activated complex should allow the reaction to occur with a low activation energy if the energy of the bond formed is sufficient to off set the energy requirements for the change from sp^ to sp^ hybrides and the loss of trigonal hyperconjugation.) Although alkyl extraction reactions are not proposed in the oxidation of hydrocarbons, it is quite possible that they occur in reactions of alkyl- boranesj however, whether they actually occur or not re mains uncertain for lack of more specific evidence.
Using the above chain carriers reactions 4 and 5 become k / (ch3)2B‘ + wall — termination k c. (CH^JgBOO* + wall — termination and the relationship k^>k^ probably arises from differences in the rate of diffusion to the wall and in reflection at the wall. The true nature of the wall in itia tio n reaction is obscure but it may readily be visualized as a wall re action in which oxygen abstracts a methyl group from t r i methylborane and the resulting dimethylboryl radical is desorbed from the wall.
Although it is possible to envision the reaction as an energy chain with excited molecules for the chain -1 6 1 -
carriers, it is difficult to reconcile this type of
reaction with wall in itia tio n since the wall should be
effective in removing the excitation energy. In view
of the near quantitative yield of peroxide it is very
improbable that the mechanism involves introduction of
oxygen atoms and therefore, it is difficult to conceive
of any other mechanisms which w ill agree with the ob
served results.
Reconsidering the correlations between reactivity
and acid strength of boron compounds, it appears that,
at least for the case of the reaction with oxygen, the
correlation stems from coordination at the wall (re
action l) and/or coordination with a radical (reaction 3)
rather than a direct coordination with oxygen in the gas
phase,
In conjunction with the results of the reaction below
the limit there are several factors to be kept in mind.
Since the oxygen was introduced into the reactor from a
higher pressure source, the in itia l mixture must have been
inhomogeneous although subjected to turbulent mixing.
Just what effect the pressure decrease caused by reaction will have cannot be ascertained. klso it is clear that
those effects described as diffusional must actually in
volve more general transport phenomena than pure diffusion.
The excessive pressure decreases obtained for experi ments at -20°G. are difficult to explain. Whether this -162-
involves adsorption or chemical processes is not clear.
The possibility of partial dimerization of the dimethyl-
borylmethylperoxide seems unlikely as the vapor pressures measurements (15) of this peroxide at this temperature do
not indicate any association in the gas phase and the re
action pressures are lower than the observed vapor
pressures. Although the data indicate a connection
between the oxygen pressure and the excess pressure
decrease it is not clear whether this is merely a rate effect or actually an indication of an interaction be
tween oxygen and the normal product of the reaction (or maybe a chain carrier).
The significance of the minor products found in this
investigation is uncertain. Since these minor products were found only in trace amounts they could have arisen from minor reactions of the oxidation or from decomposi tion of the products. Since branching would be expected to lead to new products, it appears that at the pressures investigated, branching is not important and therefore has been omitted from the mechanism. Kinetic experiments very near the limit were avoided for fear that an inad vertent explosion might affect the pressure transducer.
B. Mechanism of the Reaction at the Explosion Limit
As was seen in section V-C-2 the explosion lim it is given by the equation
_ _ _ _ a bjr— • -1 6 3 -
This same type of expression results from the following mechanism.
6) initiation —-— k 7 7) X' + 0 >Y* k8 8) I 1 + BMen — -— > a X' + products k9 9) X1 + wall ?■ termination . k10 v 10) Y* + wall ? termination
(ilote: In the above mechanism primes have been placed on the chain carriers in order to indicate that they are not necessarily the same as those given in the mechanism for the reaction below the lim it. Although the equation for the in itia tio n reaction is not written in terms of the reactants, there is nothing to preclude it from being of the same form as reaction 1 on page 158.) Assuming steady state conditions this mechanism yields the follow ing:
- k7 [x>] [o 2] ♦ a kg[Y'] [BMej) -k9 [x'J = 0 (IX) where = rate of the initiation reaction (6). i J p L k7 [xg [ o j - k8 [l'] [bMe3~] - = 0 ( X)
From £x^we obtain
k« fBMeql + kin r T , > Xi = .-8- k . _ ------iiL fY iJ (XI) k * ] ^ which substituted into equation IX yields equation XII. - 1 6 4 -
* 1*7 M (xii) [TjJ - (1-a)k7k8 [BM ejjfoJ ♦ k7k10(o2] - k8k9 [BMa3> k?k10
Substitution of XII into XI gives a solution for CxJ.
Ri ( ks [ BMe3~] + k!o) (XIII) [ i j ) (l-a)k7kg [BMe3'l [oj] + k7k1Q[o2] + kgk9 [BMe3] + k9k10
The rate of disappearance of trimethylborane, given by
equation XV will become in fin ite when 1J becomes in fin ite.
This condition w ill be fu lfille d when the denominator of
-d[BMe3] — = + kg [BMe3][Y'J (XV)
equation XII (or XIII) is equal to zero. This w ill occur
if a is greater than one (i.e., branching is occurring)
and the term (l-cOk^kg [BMe3]f o 2] has an absolute magni
tude equal to the other terms in the denominator. By
setting the denominator equal to zero, the explosion lim it
condition can be obtained.
If (l—a)kykg + k 7k10 + R8k9 3^ +
1- i r *1 k9k10 = 0 then (dividing by [BMeoj [O 2J )
(l-a)k7kg + k7k10 + ¥ 9 + k9k10 = 0 (XVI) £BMe3l ^°2J l?Me3J-[02J However reactions 9 and 10 are wall reactions and the k*s
will include diffusion terms; therefore kgk-^Q is probably
small and can be neglected. By neglecting k9k10 and
rearranging, equation XVII is obtained. -165-
1_ = (a-l)-|^- - (rT ~^ )r^T* (XVI1) [BMe3] k10 7 10 L°2j
By comparison of equation XVII with the experimental explosion limit expression r —^— = a - b i t i s PBMe3 P02 Cn_1 ) kd kskq seen that a = - - - - - and b = where the factor ET k10 7 10
P.T arises from the relation = £a J RT.
From the above relationships, it is obvious that
Arrhenius activation energy plots for the functions aT and
b will give activation energy differences for several of
the reactions involved.
Using the values of a and b given in Table 3 in
Section V-C-2 the activation energy plots were obtained
(Fig. 4.1 ). (Note: The values for a and b for the 0°C.
limit were not used as they seemed less reliable.) By using the equation/^E = - 2 . 303R (slope), the following energy differences were obtained:
AE = Eg - E ^0 = 1.0 kcal. (from log aT vs. l/T).
41E = Ey - E^o ~ (Sg - Eg) = 1.0 kcal. (from log b.
vs. l/T ).
Since reactions 9 and 10 are wall termination reactions, their activation energies would be expected to be very small. If we assume Eg = E^q = 0 then the above equations reduce to the following: Eg = 1.0 kcal.
Ey — Eg = 1 .0 k cal. - 1 6 6 -
2 .0 0
1.96 0 .5 0
0.46 .92 slope * -22!
1.88
Log aT Log b
1.84 slope ■ 216 0 .3 8
1.80 0.34
1.76 0.30 3.2 3.4 3.6 3.8 4.0 4.2
'° 3/ t
Fig. 41. Activation Energy Plot. -1 6 7 -
or Ey s 2.0 keel.
Although too much reliance cannot be placed on these
values, it seems quite certain that the reactions of this
mechanism have rather low activation energies.
As was stated in Section V-C-5 the addition of
nitrogen raises the pressure necessary for explosion.
This type of "inert" gas effect is usually attributed to
gas phase destruction of radicals in which a third body
takes part. The following are possible reactions of this
type that might be involved in the mechanism given above:
11) X' + C>2 + M product
12) Y* + BMe^ + M product
13) X* + BMe3 + M + product
14) X’ + X* + M — product
If reaction 11 is inserted in the mechanism (again ’using
the assumption that kqk^g is very small and may be neg
lected) then the explosion limit is given by the following:
_ 2 _ ( 1 _ = (a-i) i s . - r n CBMe3j k7 k10 v 7 10 > P i ] k7k10
(XVIII)
When equation 12 (but not 11) is inserted into the mechan
ism (again assuming k^k10 is small, the explosion lim it
is given by 1 fj(a‘1)^ n k8 _ , *9 /k8 r-Ton + k12 [M]\ / Tqy kl2 LMJTmT / (xl]°vtv \
Use of equation 13 with the reactions 6,7,8,9 and 10
(assuming k^k-^Q small) yields the following explosion -168- limit expression:
___1 _ = (a_ i ) - k3k9 _L_ - k,k6 M (XX) [EMej] k1Q k7kio [°23
(Note: In the above equations £mJ represents the total concentration of trimethylborane, oxygen and nitrogen.)
Reactions of the type illustrated by equation 14- will produce more complex expressions for the explosion limit. normally this type of reaction is associated with the second explosion limit of a reaction system. ho such second explosion lim it has been observed for the t r i- methylborane-oxygen system, but it may exist at pressures higher than those studied. Since these reactions are best studied at a constant fuel-oxygen ratio with varying amounts of added gas, the final conclusions regarding these reactions will have to await future investigations.
The expression given in equation XX can be compared with the observed data. The expression may be reduced to the following:
1 b cPt p = a — Tj — p • BMe3 f 02 F02
If we compare pairs of experiments in which the total pressure (Py) is the same and designate the trimethyl- borane and oxygen pressure of one of each pair with primes, then the following is obtained by subtracting one express ion from the other: (XXI)
= b + cPT where k 1 ^Me j
1 B
Using the pairs of experiments (near the lim it) given in
Table 20, this expression has been tested as shown in
Figure X.2. From this graph i t appears that equation
XXI may be obeyed and that reaction 13 is the one re sponsible for the "inert" gas effect. However, it is possible that this is a fortuitous result and something else is responsible. The other third body reactions do not yield expressions that can be readily tested with the available data and there are some other factors to be con sidered. It is possible that added nitrogen has some effect on the mixing of the reactants which is reflected in the lim it. Also there may be some competition between the "slow" reaction and the explosive reaction f'or avail able reactants. At the higher oxygen pressures (where more nitrogen was added) this competition would be expected to be greater because of the higher order for oxygen in the rate expression for the reaction below the limit. In view of a ll these factors, the author feels that the evidence for reaction 13 is not conclusive. -1 7 0 - TABLE 20
DATA FOR TESTING EQUATION XXI
EL 100a 100 a PT A x 100 B x 100 A/B Ave.Pr P (mm. ) (mm.) BMe3 p°* (mm.) (mm.)
18.86 3.38 19 34.9 6.20 1.62 3.83 34.4 107 12.66 5.00 34.0
21 21.72 2.40 46.2 6.79 0.84 8.08 46.6 97 14.93 3.24 47.1
44 22.74 1.89 57.3 4.88 0.47 10.38 59.1 95 17.86 2.36 60.9
48 22.23 2.23 48.6 7.30 1.01 7.23 47.8 97 14.93 3.24- 47.1
14.50 24 4.81 27.7 4.50 2.04 2.21 28.4 90 10.00 6.85 29.1
33 17.25 3.68 33.0 4.59 1.32 3.48 33.5 107 12.66 5.00 34.0
133 18.52 3.48 34.1 5.86 1.55 3.78 34.0 99 12.66 5.03 33.9
131 20.4.1 2.58 43.7 4.28 1.07 4.00 42.8 93 16.13 3.65 42.0
0 The second reaction of each pair is for an experi ment with added nitrogen and the pressures should be considered as the primed pressure in equation XXI. -1 7 1
9 .0
7.0
A B
5.0
3 .0
20 3 0 4 0 5 0 6 0 Total pressure (mm.)
Fig. 42. Test of Equation XXI - 1 7 2 -
The very large temperature rise which can be cal
culated for the explosion reaction (Appendix G) might
suggest that the explosion is thermal rather than chain branching. The evidence is against this. '-The reaction
rate for non-explosive mixtures follows the same laws for
mixtures close to and far from the explosion limit. If
the explosion were a thermal explosion, one might expect
a non-negligible temperature rise, and a consequent charge
in apparent kinetics, for those mixtures close to the ex
plosion limit. The virtual absence of an induction period
before explosion, the small effect of the change in geom etry to the doughnut reactor, which should change the
heat lo sses, and the agreement between the data reported here and those obtained by the very different experimental techniques of Bamford and Newitt ( 4 ), also lead to the conclusion that the explosion is not a thermal one.
Before attempting to assign specific radicals as chain carriers in the mechanism of the explosive reaction, several other factors should be considered. From the analysis of the products of the explosions (see Section
V-C-6) the following products have been identified; hydro gen, methane, carbon monoxide, carbon dioxide, ethane, ethylene, acetylene, methoxydimethylborane, trimethylbor- oxin, water and possibly traces of dimethoxymethylborane or dimethylborylmethylperoxide. From the distribution of products as a function of oxygen pressure (given in Fig. -173-
23) several relationships are evident. Considering the distribution of carbon monoxide and hydrogen, the oxida tion appears to occur in at least two separate stages - the alkyl portion of the trimethylborane is first oxidized to carbon monoxide and hydrogen and then, if su fficien t oxygen is present, these materials are oxidized to carbon dioxide and water. This is very similar to the explosive oxidation of hydrocarbons. Although l i t t l e is actually known considering the oxidation of the boron portion of the molecule, one might expect it to behave somewhat sim ilarly to carbon. If this is the case one would ex pect the boron to be oxidized to monoboron monoxide (BO) before being oxidized to boric oxide (BgO^). In regard to this it is interesting to note that if for KL 160
(mole-fraetion O 2 = O.664) no more than 0.035 mmoles of water were formed, then considering observed products there will be just enough oxygen to oxidize all the boron present to the monoxide. This assumption of the formation of monoboron monoxide has been used to calculate a probable adiabatic flame temperature (see Appendix G) which was in the neighborhood of 1000°C.
In regard to the two stage process of oxidation one would expect some overlapping of the stages and the occur rence of some by-products. From the consideration of the product distribution of explosions rich in trimethylborane, it appears that oxidation of the alkyl portion of the -174- molecule proceeds by the in itia l formation of methyl radicals which are then oxidized. A.long with this me thane, ethane and ethylene appear to be by-products, acetylene may also be a by-product of the degradation of methyl radicals, but it appears to arise from another process also as is evident from the occurrence of a maxi mum in the distribution curve (Fig. 23). Possibly the acetylene arises from the degradation of a compound of the form R-b/'II which might be formed by repeated ' OCH TT hydrogen extractions. Thus a possible reaction sequence for the production of acetylene is that illustrated by reactions 15, 16, 17, 18 and 19.
15) B(CH3)3 + R• y (CH3)2BGH2- + RH
/ GH2 16) (GH3)2BGH2* y CHoB | + H. nch 2
or / GH2 2 (CH3)2BCH2# ^ (ch (CH3)3B3)3b + + gh GH3b 1 nch 2
17) + RH 2
or
.CH > CH3BnI + ch3b II ch2 nch -175- CH R R 19) CH-.B || + R* ___} CH,BCH=CH» — ^ CHoB* + C-tU ■* ngh j
R« may be any free radical. No compounds of the type ,GH / ? h2 R-4.ll or F.-B I have been reported; however, cyclopropane GH GH2 has been reported (4-7) to be among the products of the electrolysis of an aqueous solution of lithium tetra-
methylborate, LiB(GH3)^. This suggests the formation of
carbcn-carbon bonds while the carbons are s t ill attached
to the boron and therefore gives some support to the poss
ib ility of having compounds with a three membered ring
involving one boron atom and two carboh atoms. In connec
tion with the acetylene production it is interesting to
consider the variation of the relative pressure change for
explosions near the limit with mole-fraction of oxygen
(Figs. 27 and 28). The appearance of a shoulder on the o curve for explosions at 20.1 C. was attributed to the
acetylene production. Thus the appearance of a peak rather
than a shoulder on the curve for explosions at -20.4°c = i®~
plies an increase in the production of acetylene at the
lower temperature and its formation by a process other
than the dehydrogenation of ethylene.
The only identified boron compounds in the products
from explosions were methoxydimethylborane and trimethyl-
boroxin. Whether these are intermediates in the trigger
ing mechanism of the explosion is uncertain. Nevertheless,
it seems likely that these materials are either directly -1 7 6 - involved in the reaction mechanism or result from impor tant side reactions. From the calculation of adiabatic flame temperature for some hypothetical cases (see Appen dix G), it was concluded that for lower mole-fractions of oxygen, lower flame temperatures should result. Since the yield of these materials seems greater for lower mole- fractions of oxygen (sea Table 8) they must not be the products of a high temperature reaction. Possible forma tion of these materials will be considered later in the discussion of specific chain carriers for the explosive reaction.
From equation XVII it is seen th a t the explosion limit has no relationship with the initiation of the chain carrier X! and therefore there is no known relationship between the mechanism of the reaction below the limit and that at the limit. It is possible that the same carriers are involved In both reactions or that entirely different carriers are involved. Therefore in the consideration of specific carriers for the explosive reaction emphasis is placed on the branching reaction (reaction 8). From con sideration of the low activation energy ascribed to this reaction it appears that the activated complex probably involves a coordination complex between the incoming radical (containing at least one oxygen atom) and the open sextet of the boron in trimethylborane. From consideration of the product distribution as a function of raole-fraction -1 7 7 - of oxygen and from the observation that isolation of prod ucts closely related to chain carriers is more likely at the lower mole-fraction of oxygen, it appears th at methyl radicals are involved in the mechanism and possibly are formed in the branching step. Using these two restrictions there are a number of possible chain carriers which might be Y* in reaction 8. These carriers will not be considered in connection with the rest of the mechanism and other observat ions.
20) (GH^ ) 2 h 0*2 * + B (CH ^ ) ^----£. 2 C H 3 • + ch3bo + (ch^)2bo
21) (CH^ )p BO * ----> C * + CH 3bo
22) 3CH3BO----> (CH BOj)
23) (ch3)2bo - + b (ch3)3----> (C H 3 ) 2B 0 G il 3 + B (C H 3 ) 0 •
24) (gk 3)2bo 2 - * B(CH3)3 •> ch3- + 2(CH )2B0*
25) (CH,)2B0- + 02 ----* (CKj >2BV + o.
If the triggering mechanism of the explosive reaction involves the addition of a branching step to the reaction below the limit, then the branching reaction might be reaction 20, Reactions 21 and 22 would readily explain the production of trimethylboroxin and reaction 23 would explain the presence of methoxydimethylborane in the products. This scheme of reaction 20, 21, 22 and 23 fails to agree with the general mechanism for the explosion limit which requires the regenerationcf Y1 from the -1 7 8 - reaction of X1 with oxygen. This is not possible w? th Y!
= and X' = CH^* . Although these reactions do not agree with the mechanism it is possible that they re present an accompanying minor process to the main mechan ism or that some of the individual reactions explaining the production of by-products accompany the major reaction scheme.
Reactions 2 4 and 25 are two reactions which agree with the form of the general mechanism for the reaction at the lim it. These two reactions coupled with 21, 22,
23, and reactions to be discussed later would give a fairly consistent explanation of the observed results.
Since the scheme involves the radical (CH-^pBO* as X1 then reaction 24. represents the change over step between the "slow" and the explosive reactions . Reaction 24 is more reasonable than-reaction 20 because it requires the breaking of only one B-C bond, instead of two, while forming one B-0 bond and breaking one 0-0 bond. However, reaction 25 is highly speculative and might have too high an activation energy.
A branching reaction involving the reaction of
(0112)280 * with trimethylborane seems very unlikely,
Another set of reactions which would f u l f i l l the requirements of the proposed mechanism are reactions 26 and 27. Coupled with reactions 22 and 28 they would also account for the formation of trimethylboroxin and -1 8 0 -
34) H» + 02 ----> HO* + 0*
Reactions 32 and 33 are also possible branching
reactions the chain carriers of which could be formed
by reaction 34. However, to agree with the general
mechanism it would be necessary for the methyl radicals
formed in 32 and 33 to lead to the formation of hydrogen
atoms without a net introduction of concentration terms
to the mechanism. It does not seem likely that branching would involve the reaction of a non-oxygen containing radical and trimethylborane since the low activation energy of the reaction is attributed to coordination which would involve an oxygen containing species. also it seems
unlikely that the radicals produced in the branching step are hydrogen atoms.
An examination of the mechanisms proposed shows that the essential difference between the formal reactions written for the non-explosive and for the explosive re action is that reaction 3 in a non-branching and reaction
8 a branching reaction. This either requires that X' and
Y* are different from X and Y, or else that reaction 3 produces only one chain carrier in some cases and more than one in others. Attempting extension for the latter viewpoint is to consider that reaction 3 is in fact
(gh3)2boo* + (ch3)3b (ch3).2bojch + ch )2b* and that sometimes the peroxide sp lits into free radicals, for example, as shown in reaction 35. -1 3 1 -
35) (CH3)2BuOGH3 > (CH3)2BO- + OCH-*.
The resulting boron-containing radical could then react
to form trimethylboroxin by reactions 21 and 22, or
methoxydimethylborane by reaction ?3. The metboxy radi
cals, and the methyl radicals formed in reaction 21 could
continue the development of the exploding chain.
reaction 35 could not represent the usual behavior
of the peroxide, which is known to be stable, and to de
compose mainly by rearrangement (15), but it might be
that of the unusual energy-rich molecule, assumed to have
a metastable existence. This could explain a third-body
action of added inert gas in reaction 13 as a stabilisa
tion of the aetastablc peroxide, while permitting the
chain to proceed through the radical ( 0 .4 2 )21?*. The pro
cess is then somewhat, but not exactly, analogous tc the
degenerate branching familiar to hydrocarbon oxidation,
ho similar stabilizing action is available for the reac
tion below the lim it, however, one would be forced to
conclude that the constant c of the equation on p . 158 is
not constant but includes a term (1-a)k 1 k" ^BMe^J •
inother possibility is that the change from non-explosion
to explosion is not solely due to a pressure change but does involve a heating effect at higher pressures, forming more of those peroxide molecules capable of branching, and that the explosion is chain-thermal in character.
It is possible that the actual mechanism involves -132-
combination of several of the mentioned schemes and that
the agreement between experimental observation and the
general mechanism is the result of a fortuitous simplifi
cation, Due to the highly speculative nature of several
of these reactions ana the lack of information concerning
reactions of boron containing radicals and reaction of
radicals with boron containing molecules, no attempt has
been made to estimate the energy requirements for the re
actions listed. It seems unwise to select any particular
set of chain carriers as being more likely than the
others.
G. Suggestions for Future hork
The formation of essentially one product, dimethyl-
borylmethylperoxide, in the oxidation of trimethylborane
at pressures below the explosion limit is very striking
compared to the oxidation of hydrocarbons in which a great
variety of products are formed even during the induction
period. Since this phenomenon makes it difficult to es
tablish any relationship between the chain carriers of
the "slow" and explosive reaction, it would be of interest
to study the products of reactions in the region just be
low the explosion boundry. Since a cool flame phenomenon
has been observed for the oxidation of trimethylborane (2), a study of this sort would be expected to yield interest ing products not too different from the actual chain carriers. Such a study would be made in a flow system in order that sufficient quantities of minor products could - 183- be obtained.
also it would be of :int°rest to study the explosive
reaction at much higher pressures than studied here in
order.to see if a second explosion lim it exists.
k kinetic stud;/ of the oxidation of methoxydimethyl- borane and dimethoxymethylborane would also be of interest.
The presence of a boron-oxygen bond on the parent material would help estabilize the open sextet of the boron and should result in slower rates of reaction than those ob served for trimethylborane. dith slower rates it would be easier to obtain more reliable data concerning the initial portion of the experiment. The study of the products of the reaction below the explosion limit (assum ing there is one) for these materials combined with the use of isotopes to label various groups should throw some light on the probability of various elementary reactions.
In the investigation reported herein two types of reactions have been proposed which are not very common to reactions of radicals and other organic compounds. In the case of trimethylborane these two reactions could be re ferred to as methyl displacement (reaction 35) and methyl extraction (reaction 36).
35) R* i B(CH3 )3 — >RB(CH3 )2 + GH3‘
36) ► K0CH3 + CH3)2B
(Radical displacement reactions around an unsaturated center have been demonstrated in other systems. Seiger - 1 8 4 -
and Calvert ( 4 8 ) postulated the reaction:
cf3* + ch3cocf 3 — > ch3* + (cf3 )2co
which was later confirmed by Pritchard and Steacie
(49) in the reaction:
ch3* + cf3cocf 3 — > cf3‘ + ch3cocf 3.
kIso Pitts and co-workers (50) have demonstrated the
reaction:
CD3* + Ch3CH=CHCOCK3 ---"> C4.li5D3 + Cri-jCO*.
These reactions are believed to involve the addition of
the radical to the double bond to form an intermediate
radical which splits off the ultimate radical.) In
order to prove or disprove these and other reactions
involving alkylboranes, the study of the reactions of
trimethylborane with particular radicals could be under
taken. almost any method for producing particular free
radicals such as photolysis or thermal decomposition of
particular compounds to yield essentially only one species
could be used in this type of study. These studies would
be of great importance as virtually nothing is actually known concerning elementary reactions of boron containing compounds and the proof or disproof of a given type of elementary reaction would help in the consideration of mechanisms for reaction.
In conjunction with the various studies mentioned above, the investigation and application of gas phase -185- chromatographic separation and identification of boron
compounds should not be overlooked. Due to the unusual
v o la tility of some of these compounds separation by low
temperature fractionation is not always effective. Also
the use of loop techniques for introduction of samples
on the gas phase chromatographic-column allows one to
investigate mixtures that would be too small for the
application of other methods of analysis.
t -179- methoxydimethylhorane.
26) + B(GH3)3----^ 2CH^* + CH^BO + GH^O*
27) CHcj • + 02 >
2B) C H 3 0 • + B(G K ^ ) 3 ^ CH30B(CH3)2 + CH^’
Is mentioned previously reaction 27 would be expected to involve a third body also ( 4 6 ) but in view of the ineffec tiveness of small molecules such as nitrogen and oxygen as third bodies in this type of reaction, trinethylborane would be the most likely third body. This might lead to reaction 29 rather than reactions 26 and 27 which would result in a different explosion limit expression.
Similarly, the incorporation of the reaction of methyl- peroxyl radical with oxygen to yield ozone which may then decompose to yield on oxygen atom also results in an ex plosion limit expression different from the experimental one .
Reactions 30 and 31 would be expected to involve higher activation energies than are attributed to the mechanism and therefore are not considered to be important.
30) gh3o* + b(ch3 )3 — > ch3bo + 3gh3*
31) gh3- + o2 > ch3o + 0 *
32) 0. + B(CH3 )3 ^ CH3B0 + 2CH •
33) HO. + B(CH3 )3 y CH3B0 + H- + 2CH3* V III. SUMMARY
1. Reaction of trimethylborane and oxygen in a static system at 19.9°C. at total pressures from 10 to
20 mm. yields dimethylborylmethylperoxide in almost quantitative amounts. Trace products include methane, ethane, and methoxydimethylborane.
2. Initial rates show that the order with respect to oxygen varies from 1.5 to 2.0 and the order with re spect to trimethylborane varies from 0.5 to 1.0. In each case the pressure of the other gas is a determining factor for the order with respect to the other.
3. The product(s) catalyzes the reaction.
U. Neglecting the catalytic effect, the kinetics of the reaction are approximated by the expression:
-dp kPBMe^p0p rate dt a + bPBMe^ + cP0^ where b > c>a.
5. The overall activation energy for the reaction is near zero.
6. There is a mild surface e ffe ct which is a ttrib u te d to wall initiation of the reaction.
7. Addition of added gases such as carbon dioxide, neopentane and propylene causes a reduction in the initial rate. This is believed to be a result involving transport
- 1 8 6 - -1 8 7 - phenomenon of reaction m aterials.
8. These re su lts are consistent with a mechanism that begins and ends on the wall and a possible mechanism is discussed. o 9. A.t -20.1 C. complications are noticed. The pressure decrease and oxygen consumption is somewhat larger than that predicted by the overall reaction:
b (ch3)3 + o 2 — ^ (ch3)2booch 3. k t this temperature the catalytic effect of the product(s) is not as great as at 19.9°C.
10. k t total pressures somewhat greater than those of the kinetic experiments mixtures of trimethylborane and oxygen explode. Minimum pressure for explosion occurs near 0.6 m ole-fraction of oxygen and is 21.5 mm. at 2 0.1°C. and 25.2 mm. at -20.4°C.
11. The explosion limit was determined at 25, 20.1,
0, -20.4- and -30°C, From the extensive investigation at
20.1 and -20.4°C. in an 8 cm. diameter bulb, the relation ship between the partial pressures of the reacting gps at the limit was shown to be of the form:
—p 1— = «a - b ^ p - 1 -., BMe3 02 where a and b are positive q u an tities.
12. k smaller bulb diameter resulted in a raising of the lim it indicating wall term ination. There appeared to be no great dependence on surface conditioning. -188-
13. Addition of nitrogen also raised the limit.
14. Analysis was performed on four explosions near the limit. Products included hydrogen, methane, carbon monoxide, carbon dioxide, ethane, ethylene, acetylene, methoxydimethylborane and trimethylboroxin.
15. Possible mechanisms involved in the triggering mechanism of the explosion and production of products are discussed.
16. Formation of the pyridine adduct of dimethyl- borylmethylperoxide apparently causes some induced decomposition of the peroxide which yields hydroxydi- methylborane and formaldehyde.
17. Methoxydimethylborane, hydroxydimethylborane, and oxybis(dimethylborane) were prepared by allowing trimethylborane to react with methanol or water using acetic acid as a catalyst. Reaction proceeds at room temperature in presence of the catalyst, but not at a detectable rate in the absence of the catalyst. The role of the acetic acid in these reactions is discussed. APPENDIX A
INFRARED SPECTRA OF
REFERENCE COMPOUNDS
-1 8 9 - Correction to be added to observed wave length (cm." 280 0 4 2 200 Pig. A - |. C alibration Curve for Perkin - Elmer Model 21 Spectrophotom eter eter Spectrophotom 21 Model Elmer - Perkin for Curve alibration C |. - A Pig. ra N. 178. No. erial S 1600 0 0 8 bevd ae egh n cm." in length wave Observed -190- PI. IT 0 0 4 2 3200 0 0 0 4 % TRANSMISSION g A*, nrrd pcrm f Trimethylborane of Spectrum Infrared A»*2, ig. F j i. j J& io K>MM ao 60 IPO 60 vO TRANSMISSION 0 6 g A3 Ifae Setu o Methoxydimethylborane of Spectrum Infrared A~3» ig, F CRONS N O R IC M M. I 4 1X9 — ■19 30. A
T Y MEHYBORANE N A R O YLB ETH IM XYD O ETH M -192- % TRANSMISSION g Ifae Setu o Dimethoxymethylborane. of Spectrum Infrared ig. F CR NS RO IC M 4M . 9 3 . 10 J 1 6 8D 2 MEHOXMEHYBORANE N A R O YLB ETH XYM O ETH IM D % TRANSMISSION g A5 Ifae Setu o Dmehloymethylperoxide, ethylborylm Dim of Spectrum Infrared A-5. ig. F le.sMu MEHY YMEHLEOXIDE ETHYLPERO RYLM O B YL ETH IM D h c ( 3 ) 2 h c o o b 3
-194” m.
HYDROXYOIMETHYLBOfiANE (DMETHYLBORONOUS AC®) BWH^gOH
Fig. A-6. Infrared Spectrum of Hydroxydimethylborane. % TRANSMISSION g A7. nrrd pcrm f Mxue f Hydroxydimethylborane of Mixture a of Spectrum Infrared . A-7 ig. F SSL MICRONS n Oxybis(dimethylborane). and
0 3 0 4 20 -196- % TRANSMISSION sst^ TRIMETHYLBOROXIN i. -. nrrd pcrm f Trimethylboroxin. of Spectrum Infrared A-8. Fig. MICRONS Z\ l>C Jo- 4 4 MM. 2 101 JO *9. !•SKED-.
1 61 -361- 100 NEOPENTANE 9 UM.
9 NKftONS 9 Fig. A»9® Infrared Spectrum of Neopentane
mi \ X TRANSMISSION g 41. nrrd pcrm f Pyridine of Spectrum Infrared 4^10. ig. F 101 IN. PYRIDINE APPENDIX B
MASS SPECTRA OF REFERENCE COMPOUNDS
-2 00- TABLE B-l
MASS SPECTRA OF REFERENCE COMPOUNDS
Relative Intensities (ch3)3b (ch3)2boch3 ch3b (och3)2 (ch3bo)3 (ch3)2boh (ch3)2booch3 m/<
1.9 0.8 - 5.0 1.3 1.8 11 — 0.7 0.5 12 1.4 0.9 0.5 1.5 1.0 1.7 13 - 1.1 1.2 2.7 1.2 3.3 14 1.3 31.4 23.5 12.8 6.1 100 15 — 0.8 - 2.1 0.7 2.5 16
0.3 0.5 1.1 0.6 0.3 24 1.3 1.7 0.9 3.5 1.2 2.3 25 3.9 3.4 2.1 8.3 1.8 5.5 26 6.5 4.7 2.6 3.6 2.5 8.4 27 2.1 5.1 5.5 15.0 5.4 17.0 28 - 9.0 8.0 5.1 5.5 28.1 29 - - 1.0 -— 5.6 30 - 1.0 4.1 -— 6 . 6 31 — 0.6 1.5 —— 2.2 32
2.7 1.3 mm _ m m 0.6 36 7.6 3.4 mm 1.2 0.7 1.5 37 3.4 1.3 mm 3.9 1.2 0.6 38 9.8 3.6 3.0 0.5 1.4 39 26.3 2.2 0.8 8.7 1.3 2.6 40 100 5.0 1.8 14.7 2.8 7.1 41 2.0 3.4 9.9 23.3 7.6 21.4 42 - 6.9 33.4 15.7 30.6 66.7 42 - 0.5 0.7 19.3 100 1.3 44 - - 1.5 0.7 1.3 4.4 45 TABLE B-l (continued)
Relative Intensities ( c h3) 2b o c h 3 c h3b ( o c h 3)2 ( c h3b o )3 (ch3)2boh (ch3) 2b o o c h 3 M/i
48 49 0.7 50 2.1 51 5.0 0.5 0.7 52 0.7 7.0 1.0 1.4 53 0.5 13.8 0.5 54 3.2 2.2 0.7 3.5 55 25.6 7.4 0.8 14.6 56 100 22.1 0 .8p 53.6 57 2.2 1.1 1.4p 2.4 58 2.4 4.1 59 1.0 66 7.7 67 30.6 68 43.2 69 0.7 70 O.lp 71 0.3p 24.6 7.4 72 100 30.3 73 2.4 0.7 74
0.7 81 0.6 0.7 im p.? 82 1.2 1.4 imp.? 83 2.2 84 7.7 85 TABLE B-l (continued)
Relative Intensities M/e (CH3)3B (CH3 )c>BOCH3 CH3B(OGH3 )2 (CH3BO)3 (CH^BOH (CH3 )2BOOCH3 M/e
87 - 0.6p - - 1 . 5p 87 88 - 1.9p - - 5. 8 p 88
94 - - 0.6 94 95 - - 1 .1 95 96 - - 0.8 - - 96
108 - - - 1.6 - 108 109 - - 18.1 - - 109 110 - - 73.9 - 0.8 imp.? 110 ro 111 - - 100 - 1.1 imp.? I l l S 112 - - 2.7 - - 112 I
123 - - 0. 5p - - 123 124 - - - 3 .3p - 124 12 5 - - 11. Ip - - 125 126 - - 14. 6p - - 126 127 - - 0.6 - - 127 APPENDIX C
EXPLOSION LIMIT DATA
2 04.- TABLE C-l
PRELIMINARY EXPLOSION LIMITS AT 0°C.
IN AN 8 CM. DIAMETER BULB
Notebook In itia l Pressures Final RF 2114 PEL Explosion? Pres sure Page (mm?)3 (mm. ) (mm.)
134 1 5.0 14.2 No 135 2 10.5 - 21.1 Yes 52.5 135 3 5.2 19.5 Yes 39.5 136 4 11.3 15.7 Yes 53.1 136 5 11.4 13.4 N o 13.2 137 6 17.2 9.8 No 17.2 137 7 17.0 12.9 N o 17.3 137 8 17.1 17.0 Yes 49.4 138 9 22.1 10.8 No 22.7 138 10 20.5 15.3 Yes 52.1 TABLE C-2
PRELIMINARY EXPLOSION LIMITS AT 0°C.
IN A 4.5 CM. DIAMETER BULB
Notebook In itia l Pres sures Final RF 2114 PEL b (ch3)3 °2 Explosion? Pressur Page (mm. ) (mm. ) (mm. )
140 11 5.5 5.5 No 7.5 140 12 6.0 12.7 No 18.8 141 13 6 .4 20.3 No 28.8 141 14 6.9 33.5 No 33.5 141 15 11.7 15.6 No 18.5 142 16 13.0 20.1 No 23.5 142 17 11.8 37.1 Yes 50.0 142 18 9.0 21.5 No 22.5 142 19 15.5 21.1 Yes 42.4 143 20 16.7 14.7 No 19.5 143 21 18.4 15.4 N0 24.0 143 22 18.3 23.1 Yes 57.0 144 23 8.8 31.4 No 30.9 144 24 8.5 33.7 Yes 40.9 144 25 11.3 28.2 Ye s 52.5 144 26 6.5 40.5 No 40.0 149 27 8.5 33.0 No 31.9 149 28 8.5 34.8 No 39.4 149 29 9.5 41.7 Yes 37.3 150 37 19.8 19.3 Yes 45.0 150 38 18.9 16.0 No 23.6 TABLE C-3
PRELIMINARY EXPLOSION LIMITS AT 0°C. IN A 4.5 CM.
DIAMETER BULB USING AIR AS A SOURCE OF OXYGEN
N otebook In itia l Pressures Final RF 2114. PEL b (ch3 )3 Air O2 Explosion? Pressuri Page (mm. ) (mm.) (mm.) (mm. )
150 30 9.4 125.9 26.7 No 129.3 150 31 9.4 157.6 33.4 No 160.1 150 32 10.0 188.6 40.0 No 193.9 150 33 10.4 221.5 47.0 No 229.4 150 34 10.4 286.0 60.6 No 285.5 150 35 18.1 216.3 45.9 Yes 239.5 150 36 9.8 330.8 70.1 No 324.6 150 39 18.8 186.5 39.5 Yes 207.5 -2 0 3 - TABLE C-4
PRELIMINARY EXPLOSION LIMITS AT -30°C
IN AN 8 CM. DIAMETER BULB
Notebook ....In itia l Pressures Final C-l PEL Explosion? Pres sure ]»(« j ^*2 Page (mm. ; (mm. ) (mm.)
89 40 5.0 No 35 90 41 5.0 129 No 12 0 90 42 11.0 70 Yes 40 90 43 12.0 38 Yes 65 91 44 11.0 23 Yes 59 91 45 9.0 inc ompl .ete, equipment failure 94 46 10.0 6 No - 95 47 10.5 incomplete - - 95 48 9.0 16 No 16 95 49 10.5 15 No 15 96 50 9.0 22 Yes 54 96 51 10.0 18 No 18 96 52 10.8 26 Yes 64 97 53 15.2 13 No 17 97 54 15.2 25 Yes 67 99 55 5.5 18 No 20 99 56 5.7 25 No 23 100 57 6.0 24 No 23 100 58 5.8 55 No 50 100 59 5.5 56 No 52 101 60 6. 5 101 N0 92 101 61 5.7 126 No 117 101 62 5.3 166 Yes 153 102 63 7.5 85 Yes 57 102 64 7.5 71 Yes 45 102 65 5.8 58 Yes 39 103 66 4.8 47 No 44 103 67 4.8 66 No 61 103 68 5.5 123 No 116 104. 69 6.0 69 Yes 48 104 70 6.5 43 Ye s 23 104 71 6.0 21 Yes 31 105 72 6.5 24 No 23 105 73 7.5 20 No 21 105 74 7.8 33 Yea 38 -2 09- TABLE C-5
PRELIMINARY EXPLOSION LIMITS AT 25°C.
IN A 8 CM. DIAMETER BULB
Notebook In itia l Pressures Fi E—1 PEL b (ch3)3 ^2 Explosion? Pre Page (mm. ) (mm. )
107 75 5.2 21 Yes 27 108 76 5.5 9 No 12 108 77 4.9 21 Yes 29 108 78 5.5 10 No 11 108 79 6.8 8 No 13 109 80 7.5 9 No 12 109 81 7.8 16 Yes 44 109 82 3.2 13 No 10 109 83 3.0 18 No 12 110 84 6.9 18 Yes 42 110 85 7.0 13 No — 110 86 9.6 10 Yes 36 110 87 15.0 15 Yes 49 -2 1 0 -
TABLE C-6
EXPLOSION LIMITS AT -20.4°C. IN AN 8 CM. DIAMETER BULB
Notebook In itia l Pressures Fina C-l EL b(ch3)3 °2 Explosion? Pres su Page (mm.) (mm. ) (mm.
147 0 12.3 10.2 No — 147 0 13.4 (4 .2 )a Yes (48.2 Notebook C-2 Page 19 1 11.4 inc omplete 19 2 10.8 13.6 No — 20 3 14.6 (4.8) 8 Yes (48.1 24. 4 6.7 3.3 No - 25 5 12.2 7.9 No — 25 6 4.2 7.5 No - 25 7 9.4 14.7 No - 26 8 7.6 1.6 No _ 26 9 7.3 111.6 Yes 40.6 26 10 14.0 14.5 Yes 56.0 27 11 5.3 — No — 27 12 7.0 7.3 No — 27 13 12.5 17.2 Yes 61.7 28 14 0.8 19.5 No — 28 15 10.2 18.4 Yes 58.1 28 16 6.6 15.1 No _ 29 17 3.4 25.1 No - 30 18 8.1 13.5 No — 30 19 5.3 29.6 Yes 21.1 . 30 20 11.1 inc omple ' +V Q 21 4.6 41.6 Yes 22.2 31 22 9.1 25.6 Yes 49.4 32 23 2.9 32.5 No — 32 24 6.9 20.8 Yes 41.4 32 25 1.4 36.6 No 33 26 9.3 23.8 Yes 63.5 34 27 3.8 26.8 No 0 m 34 28 9.1 26.4 Yes 59.8 35 29 3.8 29.9 No 35 30 8.1 20.0 Yes 53.2 35 31 2.7 38.4 No 36 32 16.3 17.1 Yes 62.3 36 33 5.8 27.2 Yes 23.6 41 34 2.3 74.8 No
a These values may be in error as the reaction st< cock turned rather slowly and may have s t i l l been opened when explosion occurred. After EL 3 the reaction stopcock was regreased. -2 1 1 - TABLE C-6 (continued)
Notebook I n itia l Pressures Final C-2 EL b (ch 3) 3 °2 Explosion? Pres sure Page (mm. ) (mm. ) (mm.) 42 35 8.6 25.0 Yes 53.0 42 36 3.3 53.2 No - 42 37 11.6 17.4 Yes 57.4 43 38 5.2 14.6 No - 43 39 9.2 14.2 No - 43 40 5.4 24.8 No - 44 41 11.3 12.0 No - 44 42 5.1 27.0 No - 48 43 11.9 11.8 No - 48 44 4.4 52.9 N 0 - 48 45 15.4 15.4 Yes 60.0 49 46 3.8 47.7 No - 50 47 16.8 18.4 Yes 65.5 50 48 4.5 44.1 No - 50 49 12.6 17.7 Yes 60.1 51 50 4*4 49.6 No 53 51 17.8 10.1 No b — 53 52 5.2 53.6 No b — 53 53 11.2 9.8 No b — 54 54 5.8 20.5 No b — 54 55 10.8 12.1 No b — 54 56 5.9 27.0 No b — 58 57 16.3 17.7 Yes 65.6 59 58 7.5 16.1 No 59 59 13.1 10.6 No — 61 60 5.0 21.1 No 62 61 14.2 9.3 Nn 63 62 5.5 26.5 N0 _ 63 63 17.3 11.5 No — 64 64 8.4 27.0 Yes 49.1 64 65 16.3 19.7 Yes 102.7 64 66 4.0 60.4 No 79 67° 11.1 10.9 No — 79 68° 4.8 24.8 No 79 69 c 17.2 13.6 No 81 70 c 4.2 23.0 No 71 c 81 15.9 13.2 No 161 108° 8.1 8.3 No 164 109 c 4.0 18.9 No 168 110° 5.9 29.1 Yes 19.6 b These experiments not reliable because phototube was turned within housing. c These experiments performed in a clean vessel. -2 1 2 - TABLE C-6 (continued)
Notebook In itia l Pressures Final C-2 EL b (ch3)3 Explosion? Pressur' Page (mm. ) (mm. ) (mm. )
168 111 6.7 30.5 Yes 24.0 169 112 4.5 16.6 No - 169 113 14.7 12.2 No - 170 114 3.8 33.4 No - 170 115 4.5 37.5 No — 171 116 4.2 37.7 No - 171 117 4.2 47.5 No - 172 118 7.2 26.2 Yes — 175 — 119 d 7 a 14.6 No 175 119-P 10.9 No — 181 132 9.6 17.3 Yes 56.7 182 133 5.4 28.7 Yes 19.9 183 134 12.0 11.4 No — 183 135 12.9 16.2 Yes 59.0 184 136 13.1 15.0 Yes 54*4 184 137 11.4 13.5 No 185 138 14.5 14.1 Yes 58,4 185 139 13.4 12.3 No _ 186 140 13.0 11.1 No _ 186 141 13.6 14.2 No 186 142 20.9 12.7 Yes 58.3 187 143 7.9 21.4 Yes 48.5 187 144 6.4 14.8 No 188 145 6.3 17.5 No -
^ This experiment performed by adding oxygen to the products of the previous experiment. -213- TABLE C-7
EXPLOSION LIMITS AT -20.4°C . IN AN 8 CM. DIAMETER BULB
USING A 76.6 PER GENT OXYGEN IN NITROGEN MIXTURE AS A
SOURCE OF OXYGEN
N otebook Initial Pressures Final C-2 EL B ch3 3 °2. Explosion? Pressure Page (mm. ) (mm. ) (mm. )
82 72 3.9 ? 23.2 No 82 73 16.1 b 15.9 Yes 73.5 88 74 4.9 25.1 No - 89 75 16.0 12.0 No - 89 76 3.8 26.1 No - 90 77 16.3 11.7 No - 90 78 4.0 33.4 No - 91 79 7.9 14.1 No — 91 80 4.8 27.4 No — 91 81 16.1 11.1 No — 92 82 6.7 12.3 No — 92 83 18.1 14.2 Yes 62.3 93 84 8.2 11.7 No .. 94 85 5.1 28.6 No — 94 86 15.6 15.9 Yes 60.4 95 87 7.7 18.1 Yes 49.7 95 88 5.4 23.7 No — 95 89 7.3 17.0 No — 95 90 10.0 14.6 No _ 96 91 6.4 17.3 No j ra O '? A n — ✓ f 4. ( 33.6 No 97 93 6.2 27.4 No 98 94 10.9 13.2 No — 98 95 5.6 42.4 No MB 99 96 7.2 13.9 No 100 97 6.7 30.9 Yes 34.4 102 98 8.6 17.2 No 103 99 7.9 19.9 Yes 55.7 105 100 10.6 20.5 Yes 74.7 106 101 6.6 26.3 Yes 37.7 107 102 10.4 12.0 No 107 103 7.3 17.2 No 108 104 15.4 12.5 No 108 105 8.5 15.5 No 111 106 15.3 12.7 No m m 111 107 7.9 20.0 Yes 57.1
® Final pressure excludes nitrogen pressure. d These experiments performed in a clean vessel. -2 1 4 - TABLE C-8
EXPLOSION LIMITS AT 20. 1°C. IN AN 8 CM. DIAMETER BULB
Notebook In itia l Pres sures Final C-2 EL b (ch3)3 °2 Explosion? Pressu: Page (mm.) (mm. ) (mm. )
2.02 146 6.7 24.2 Yes 39.6 203 147 7.0 18.4 Ye s 44 • 0 206 148 5.3 15.4 No - 2 07 149 8.3 13.7 Yes 42.7 2 07 150 10.6 12.2 Yes 41.7 2 08 151 7.9 11.8 No - 210 152 11.1 8.0 No - 211 153 9.2 12.1 Yes 40.4 214 154 6.6 13.7 No - 216 155 10.2 11.9 No - 217 156 9.1 14.5 Yes 44.6 229 157 6.2 18.8 Yes 33.1 2 31 158 5 .i 21.2 No - 235 159 6.7 15.2 No - 238 160 7.5 14.8 Yes 46.0 245 161 9.7 12.4 Yes 40.2 256 162 14.2 11.8 Yes 44 • 6 257 163 13.7 10.8 Yes 39.6 265 164 14.1 8.9 No — 269 165 4.9 22.5 Yes 17.2 275 166 14.3 7.8 No - 276 167 15.0 8.8 No — 278 168 14.4 11.5 Yes 42.6 282 169 14.4 10.1 Yes 32 .1 283 170 13.1 9.1 No _ 283 1704Pa 15 .-6 ^ ^ No — 285 171 11.0 11.0 No - 288 172 12.1 11.3 Yes 41.0
a This experiment performed by adding oxygen to the products of the previous reaction. APPENDIX D
GAS PHASE CHROMATOGRAPHIC ANALYSIS
- 2 1 5 - 1
-2 1 6 -
The gas phase chromatography data reported in this
appendix were obtained using the 16 foot Molecular Sieve
and 8 foot S ilica Gel columns and techniques described in
the Ph D0 d issertatio n of G. H. Hembree (34-). The
average retention times for the peaks normally studied
with these columns are lis te d in Table D-l.
Table D-l
RETENTION TIMES FOR GAS PHASE CHROMATOGRAPHY PEAKS
16 foot Molecular Sieve Column at 75°C. and Helium Flow of 25 cc./m in.
Feak Ave. Detention Time (m in.)
Hydrogen 4.0 Oxygen 7.7 Nitrogen 14*9 Methane 21.3 Carbon Monoxide 47.1
8 foot Silica Gel Column at 75°C. and a Helium Flow of 25 cc./m in.
Peak Ave. Retention Time (min.)
Air 2,5 Ethane 1 1 .1 Carbon Dioxide 14*0 Ethylene 19.9 Acetylene 40.3
C alibration factors for the various peaks were ob
tained by use of the standard gas mixtures described in
Sections III—E—1 and III—E—2. The determination of the
calibration factors with samples o,f different size -2 1 7 -
indicated that the calibration was linear but with a fair
degree of scatter as can be noted in Table D-2.
The determination of the composition of the non-
condensable and C2 fractions of the products of four
explosion experiments is illustrated in Tables D-3 and
D-4 . The amounts mentioned in the "Sample* column of
these tables indicate the amount of the sample placed
on the gas phase chromatography column and not the to ta l
size of the fraction in question. The per cent compos
ition is based on the total amount found rather than on
amount originally put on the column. Discrepancies
between amount found and amount introduced on the column
may have arisen from misreading the pressure in the
sample loop, extended introduction of sample onto the
column (possibly caused by improper sweeping of the sample loop), by absorption of the gases by stopcock grease, or by sh ifts in the calibration.
The results of the analysis are summarized in Tables
D-5 and D-6 and have been used in Section V-C-6-c. TABLE D-2
CALIBRATION FACTORS FOR GAS PHASE CHROMATORGRAPHY PEAKS
Molecular Sieve Column Silica Gel Column Sample Size Sample Size of Standard Calibration Factors of Standard Calibration Factors Mixture micromoles/mm. peak height Mixture micromoles/mm. peak height (micromoles) ch4 CO (micromoles) c2h6 co2 H2 c 2h4 C2H2
8.0 1.35 0.116 0.264 23.3 0.0564 0.0842 0.0983 0.263 15.1 1.27 0.118 0.262 31.2 0.0516 0.0766 0.0868 0.219 18.4 1.12 0.110 0.233 34.6 0.0550 — a 0.0941 0.248 19.9 1.34 0.112 0.235 46.7 0.0564 0.0740 0.0899 0.228 25.6 1.44 0.116 0.245 36.2 1.35 0.116 0.236 Average 1.31 0.115 0.246 Average 0.0539 0.0799 0.0923 0.240
a Instrument failure distorted peak -2 1 9 - TABLE D-3
GAS PHASE CHROMATOGRAPHIC ANALYSIS OF NON-CONDENSffBLE FRACTIONS
Peak Total Sample Peak Height Micro Micro % (mm.) moles moles C ompi Found Found
EL 160 h2 12.0 15.72 55.2 (29.5 micro CH. 3.0 0.34 28.48 1.2 moles) CO** 50.5 12.42 43.6
EL 161 H2 12.0 15.72 59.3 Sample 1 25.5 2.93 26.52 11.0 (29.6 micro CO 32.0 7.87 29.7 moles )
EL 161 H2 13.0 17.03 57.1 Sample 2 ch4 29.0 3.34 29.84 11.3 (35.0 micro CO 38.5 9.47 31.7 moles )
EL 163 H2 12.0 15.72 53.4 (29.0 micro CH. 83.0 9.54 29.44 32.4 moles ) CO4 17.0 4.18 14.2
EL 165 H2 3.0 3.93 20.0 (18.3 micro °2 6.5 0.30 a 19.61 1.5 moles ) ch4 0.0 - _ co4 62.5 15.38 78.4
Q Calibration factor for oxygen is 0.047 micromoles/mm. peak height. -2 2 0 - TABLE D-4
GAS PHASE CHROMATOGRAPHIC ANALYSIS OF C2 FRACTIONS
Total Peak Micro Micro % Sample Peak Height moles moles C ompi (mm.) Found Found
EL 160 C2H6 2.0 0.11 4.3 (3.04 micro co 2 8.5 0.68 2.58 26.4 moles) g 2h4 2.5 0.23 8.9 C2H2 6.5 1.56 60.5
EL 161 c2h6 5.5 0.30 3.5 (8,4.8 micro C02 4.5 0.36 8.52 4.2 moles) C2 H4 8.5 0.78 9.2 c2h2 29.5 7.08 83.1
EL 163 c2h6 46.0 2.48 14.2 (18,6 micro COo 7.0 0.56 17.45 3.2 moles ) 82.0 7.57 43.4 C2H2c2h4 28.5 6.84 39.2
EL 165 c2 h6 0.0 (24,4 micro go2 off scale 22.4 22.4 100 moles) C2*4 0.0 44 0.0 TABLE D-5
SUMMARY OF ANALYSIS OF NON-CONDENSABLE FRACTIONS
Pere ent Composition Composition (mmoles ) Experiment Total Amount (mmoles) h2 °2 ch4 CO h2 o2 ch4 CO EL 160 0.684 55.2 mm 1.2 43.6 0.378 0.008 0.298 EL 161 0.522 58.2 — 11.1 30.7 0.304 - 0.058 0.160 EL 163 0.473 53.4 - 32.4 14.2 0*253 - 0.153 0.067 EL 165 0.138 20.0 1.5 - 78.4 0.028 0.002 - 0.108
TABLE D-6
SUMMARY OF ,ANALYSIS OF C2 FRACTIONS
Experiment Total Amount Percent Composition Composition (mmoles ) O O (mmoles) CM co2 c2h6 c2h4 C2H2 c2h6 C2*4 c2H2
EL 160 0.012 4.3 26.4 8.9 60.5 0.0005 0.0032 0.0011 0.0073 EL 161 0.074 3.5 4.2 9.2 83.1 0.0026 0.0031 0.0068 0.061 EL 163 0.086 14.2 3.2 43.4 39.2 0.0124 0.0027 0.0371 0.034 EL 165 0.114 - 100 -- - 0.114 - - APPENDIX E
KINETIC EXPERIMENT DATA
-222 In th is appendix the results of each individual
kinetic experiment have been summarized in table form.
Each table (consisting of two experiments) is divided
into three parts. The f ir s t section contains the data
necessary to calculate the initial oxygen pressure in
the reaction vessel; the second gives the in itia l tr i-
methylborane pressure, and/or the total reaction mixture
pressure prior to introduction of oxygen (this latter
pressure refers to added gas experiments) and the pressure
time data: and the last section summarizes the treatment
of the reaction products.
This last section usually consists of the results of
fractionating the mixture into three (or four) parts by
pumping off non-condensables (reported as oxygen although
nitrogen from the original oxygen supply and traces of
methane were present) and fractionating through traps at
-118, -14.2 and -196°C. (Sometimes a trap at -155°C. was
also used.) In those few cases where a -155° trap was
used, the material collected at -196° was normally design
ated as the C2 fraction and in some cases was identified
as ethane by gas phase chromatography. The material
collected in the —155° trap (or the -196 trap when the 0 —155 trap was not used) was designated as trimethylborane
That this was the case was confirmed by obtaining mass
spectra. (The C2 fraction was usually negligible compared to the trimethylborane; thus failure to separate the 02*3 -2 24.-
has no effect on the value for the mmoles of trimethyl- borane recovered). The peroxide was determined by an
iodometric procedure discussed in Section VI-B-3.
In order to conserve space the following notations
have been used throughout the tables of this appendix.
R represents type of vessel and temperature.
I represents the in itia l oxygen reading on the oil manometer.
F represents the fin a l oxygen reading on the oil manometer.
d represents the density of DC 703 oil at room tem perature (given in parenthesis).
Pj^O^ "k*18 initial oxygen pressure in the reactor which is calculated by substitution of the values of the
items into the equation given in Section VI-B-1.
A represents the meter reading X 10.
B represents the time in seconds.
C represents the pressure in the reactor. The first value under C gives the initial trimethylborane pressure
(except for experiments, which start with product(s) of the previous reaction). The pressure at zero time is the total of the initial trimethylborane pressure, the pressure of any added gases and the calculated value of
PE02 ‘ Calculation of initial amounts of gases may be per formed by use of the following equation: I
-225- PV mmoles of gas = ' ~
where P = pressure of gas in cm.
V = 285.3 for spherical reactor
V = 247.3 cc. for cylindrical doughnut reactor
A = 1827 cm.cc./mmole when t = 19.9°C.
A = 1578 cm.cc./mmole when t = -20.1°C.
The calibrations of the pressure transducer have
been included in this appendix in the form of graphs.
In normal operation the calibration was checked weekly
and little change was noticed in the calibration unless
the temperature was changed. Because of this temperature
effect it was customary to recalibrate after every tem
perature even though only two different temperatures
were used. Except for a shift caused by a change in the
circuit between the 2nd and 3rd calibrations, the cali
brations for the same temperature show only minor sh ifts.
Calibration no. 6 was made on a different scale reading
on the voltmeter to allow for measurement of high
pressures needed in performing K-39. In all 8 different
calibrations were obtained and each calibration is placed
between the tables of the experiments between which the
calibration was made. Meter reading x 10 20 5 0 5 20 15 10 5 0 i . -. rndcr airto N.I Tmeaue I9.9°C. Temperature No. CalibrationI, Transducer E-l. Fig. rsue (mm.) Pressure 6- -22 7- TABLE E—1
DATA FOE EXPERIMENTS K-l AND K-2
Experiment K-l Experiment K-2 R Spherical 19.9 C. Spherical 19.9°C. I 196.5 185.8 F 150.4 145.3 o d 1.0692(24.5°C.) 1.0684(25.5 C.) 6.0 mm. pr °2 5.3 mm.
A B C AB G (sec. ) (mm.) (s e c .) (mm.)
1.8 — 5.2 1.8 5.2 8.0 5.2 11.0 7.5 2 10.5 7.0 15.5 10.1 6.5 13.2 9.6 6.5 22.5 9.6 6.0 21.3 9.1 6.0 31.4 9.1 5.5 30.8 8.7 5.5 42.7 8.7 5.0 43.6 8.2 5.0 57.0 8.2 4.5 61.4 7.8 4.5 76.0 7.8 4.0 82,5 7.3 4.0 101 7.3 3.5 110.2 6.8 3.5 147 6. 8 3.0 158.3 6.4 3.0 208 6.4 2.5 238.5 5.9 2.8 300 6.2 2.2 353.5 5.5 2.4 540 5.8 2,0 598 5.4 2.4 930 5.8 1.9 900 5.3
Oxygen 0.010 mmoles Oxygen 0.0008 mmoles Trimethyl Trimethyl borane Not measured borane Not measured Peroxide 0.078 mmoles Peroxide 0.0693 mmoles TABLE E-2
DATA FOB. EXPERIMENTS K-3 AND K-4
Experiment K-3 Experiment K-4Q R Spherical 19.9 °c. Spherical 19.9 C • I 312.0 263.0 F 230.2 193.6 d 1.0700(23.5 c.) 1.0692(24.5°C. ) PR0 10.& mm. 9.1 mm. 2
ABC A B C (sec. ) (mm. ) (sec. ) (mm. )
1.7 5.1 1.8 5.2 13.0 2.2 15.3 12.0 2.2 14.5 11.0 13.3 13.6 10,0 11.2 12.7 10.0 21.0 12.7 9.0 18.7 11.8 9.0 33.2 11.8 8.0 29.9 10.9 8.1 63.5 11.0 7.0 51.4 10.0 8.0 79.2 10.9 6.5 70.6 9.6 7.9 490 10.9 6.1 123.8 9.2 6,0 795 9.2
Oxygen 0.0903 mmoles Oxygen 0.0638 mmoles Trimethyl Trimethyl borane Not measured borane 8 0.0006 mmoles Peroxide 0.0745 mmoles Per oxide 0.0742 mmoles
q This fraction contained traces of peroxide, noted by reaction with the mercury in the Toepler pump. TABLE E-3
DATA FOR EXPERIMENTS K-5 AND K-6
Experiment K-5 Experiment K-6 R Spherical 19.9°C. Spherical 19.9°C. I 239.9 257.3 F 2.88.9 209.3 d 1.0662(28.0°C.) 1.0649(29.5°C.) PR0o 6.7 mm. 6.3 -mm.
AB C A B C (sec. ) (mm. ) (sec.) (mm. )
4.2 — 7.5 4.2 7.5 11.0 5.5 13.6 11.0 3.1 13.6 10.0 12.1 12.7 10.0 9.6 12.7 9.0 20.8 11.8 9.0 18.2 11.8 8.0 33.0 10.9 8.5 24.2 11.4 7.4 42.5 10.4 8.0 29.5 10.9 7.0 52.0 10.0 7.5 36.4 10.5 6.5 66.4 9.6 7.0 45.5 10.0 6.0 84.1 9.1 6.5 57.6 9.6 5.0 144.8 8.2 6.0 72.0 9.1 4.2 Final 7.5 5.5 92.8 8.7 5.0 127.3 8.2 4.7 177.5 8.0 4.5 223.9 7.8 4.2 460 7.5
n nnnrr W. "1 ~ « n aaac r ___i Oxy g© xi V/ » w v I I U U 1 U X D 0 go 11 IIIXUUXC Trimethyl Trimethyl borane 0.0172 mmoles borane Not measured Peroxide 0.0931 mmoles Peroxide a 0. 0661b
a Infrared spectrum obtained, agreed with that previously obtained by Petry (15)j however, small amount of trimethylborane present was masked out by larger ab sorption of peroxide. b This value low, because of trimethylborane inter ference. - 2 3 0 - TABLE E-4
DATA FOR EXPERIMENTS K-7 AND K-8
Experiment K-7 Experiment K-8 R Spherical 19. 9°C. Spherical 19.9°C. I 209.3 140. 8 F 178.7 123. 9 0 d 1.0645(30.0 °c.) 1. 0645(30.0 C.) p 7.5 mm. 2. 2 ram. 2
A B c A B C (s e c .) (mm. ) (s e c .) (mm. )
4.2 •• 7.5 3.6 6.9 8.5 4.5 11.4 6.0 1.6 9.1 8.0 12.2 10.9 5.7 15.4 8.9 7.5 20.1 10.5 5.4 24.3 8.6 7.0 30.4 10.0 5.2 35.4 8.4 6. 5 43.5 9.6 5.0 51.5 8.2 6.2 52.3 9.3 4.8 78.4 8.0 6.0 60.5 9.1 4.5 99.7 7.8 5.5 86.0 8.7 4.1 149.7 7.4 5.0 124.6 8.2 4.0 179.5 7.3 4.5 195.6 7.8 3.6 600 6.9 4.2 540 7.5
Oxygen 0,00044 mmoles Reaction mixture le f t Trimethyl in reaction vessel for borane a 0,056 mmoles next experiment. Peroxide 0.0560 mmoles
a Contained small amount of C2 hydrocarbon(s). -231- TABLE E-5
DATA FOR EXPERIMENTS K-8-P AND K-9
Experiment K-8-P Experiment K-9 R Spherical 19.9°C Spherical 19.9°C I 212.4 253.0 F 171.9 209.5 d 1.0645(30.0°C. ) 1.0654(29.0°C.) PR0_ 5.3 mm. 5.7 mm. 2
A B c A B C (sec. ) (mm. ) (sec. ) (mm. )
3.9 — 7.3 8 7.0 _ 10.0 9.3 3 12.1 13.0 5.0 15.3 8.5 10.6 11.4 12.0 11.6 14.5 8.0 16.4 10.9 11.0 19.8 13.6 7.5 23.0 10.5 10.5 25.0 13.2 7.0 33.2 10.0 10.0 31.5 12.7 6.5 45.6 9.6 9.5 39.3 12.3 5.5 61.5 8.7 9.0 49.0 11.8 5.0 83.5 8.2 8.5 62.6 11.4 4.8 146.8 8.0 8.0 83.5 10.9 4.5 179.5 7.8 7.5 115.5 10.5 4.0 360 7.3 7.0 2 64 10.0 3.9 1320 7.3 7.0 480 10.0
Oxygen 0.0069 mmoles Oxygen Not measured Trimethyl Condens- borane 0.0001 mmoles ables Accumulated Per oxide 0.1009 mmoles
a This corresponds to 4.7 mm. of trimethylborane and 2.2 mm. of dimethylborylmethylperoxide. TABLE E-6
DATA FOR EXPERIMENTS K-10 AND K -ll
Experiment K- 10 Experiment K-ll R Spherical 19. 9°C. Spherical 19.9°C • I 318.6 336.1 F 263.1 274.3 a 1.0654(29.0 °c.) 1.0645(30.0°C. ) p 8.1 mm. RO 7.3 ram. 2
AB c A BG (s e c .) (mm.) (sec. ) (mm.)
4.2 7.5 4.2 7.5 12.5 2.5 14.9 13.5 2.5 15.8 11.0 9.2 13.6 12.0 7.9 14.5 10.0 15.4 12.7 11.0 12.9 13.6 9.0 24.1 11.8 10.0 18.9 12.7 8.0 36.9 10.9 9.0 28.0 11.8 7.0 56.5 10.0 8.0 41.2 10.9 6.5 68.9 9.6 7.5 50.2 10.5 6.0 39.1 9.1 7.0 62.0 10.0 5.5 113.3 8.7 6.5 77.5 9.6 5.0 169.0 8.2 6.0 98.4 9.1 4.5 284 7.8 5.5 132.7 8.7 4.2 480 7.5 5.2 171.8 8.4 5.0 238 8.2 4.8 300 8.0 4.6 42 0 7.9
Oxygen Not measured Oxygen Not measured Condens- Condens- ables Accumulated ables Accumulated -233- TABLE E-7
DATA FOR EXPERIMENTS K-12 AND K-13
Experiment K-12 Experiment K-13
R Spherical 19.9°C. Spherical 19.9°C • I 223.0 202.9 F 177.1 162.9 d 1.0654(29.0°C.) 1.0658(28.5°C. ) P„n 6.0 mm. 5.2 mm. 2
A B c AB G (s e c .) (mm. ) (sec. ) (mm. )
4.2 7.5 2.6 6.0 11.0 2.2 13.6 8.0 3.9 10.9 10.0 8.0 12.7 7.5 9.4 10.5 9.0 16.5 1 1 .8 7.0 15.5 10.0 8.5 22.2 11.4 6.5 23.0 9.6 8.0 28.1 10.9 6.0 33.2 9.1 7.5 36.6 10.5 5.5 44.5 8.7 7.0 46.5 10.0 5.0 62.4 8.2 6.5 58.6 9.6 4.5 83.0 7.8 6.0 75.7 9.1 4.0 110.8 7.3 5.5 -99.9 8.7 3.5 154 6.3 5.0 138 8.2 3.0 256 6.4 4.5 233 7.8 2.6 540 6.0 4.3 3 60 7.6 4.2 600 7.5
Oxygen Not measured Oxygen Not measured Condens- Condens- o V»1 a a A MO. V w c c uni ul s ted ables Accumulated Trimethyl borane Not measured (K-ll through K-13) Peroxide 0.442 mmoles (K-ll through K-13) -2 34- TABLE e - s
DATA FOE EXPERIMENTS K-14 AND K-15
Experiment K-14 Experiment K-15 R Spherical 19. 9°C. Spherical 19.9°C • I 264.2 311.8 F 217.5 260.4 d 1.0662 (28.0°C. ) 1.0658(28.5°C. ) mm. 6.8 mm■ • pro2 6,1
AB c A B C ( s e c .) (mm. ) (sec. ) (mm. )
1.8 — 5.2 4.2 7 *5 h 7.0 — 10.0 a 10.2 — 12.9 b 14.0 1.5 16.2 18.5 3.2 19.8 13.0 10.6 15.3 17.0 11.1 18.6 12.0 22.5 14.5 16.0 18.0 17.8 11.5 29.6 14.0 15.0 26.7 17.0 11.0 38.7 13.6 14.5 32.9 16.6 10.5 50.0 13.2 14.0 40.0 16.2 10.0 64.9 12.7 13.5 48.4 15.8 9.5 83.0 12.3 13.0 59.0 15.3 9.0 105.9 11.8 12.5 73.3 14.9 8.5 154.7 11.4 12.0 94.7 14.5 8.0 238 10.9 11.5 103 14.0 7.8 369 10.8 10.2 480 c 12.9 7.7 600 10.7 10.2 720 12.9
Oxygen Not measured Oxygen Not measured Condens- C ondens- ables Accumulated ables Accumulated
a This corresponds to 4.8 mm. of carbon dioxide, k This corresponds to 5.4 mm. of carbon dioxide. c Watch accidentally stopped and started again. TABLE E-9
DATA FOR EXPERIMENTS K-16 AND K-17
Experiment K-16 Experiment K-17 R Spherical 19.9°C. Spherical 19.9°C. I 288.2 245.5 F 254.4 203.3 d 1.0649(29.5°C.) 1.0670(27.0°C.) 4.4 mm. 5.5 mm.
A BC AB C (s e c .) (mm. ) (sec. ) (mm.)
1.8 5.2 7.0 10.0 12.8 - 15.2 a 13.1 2.8 15.4 18.0 1.8 19.4 12.0 10.8 14.5 17.5 9.5 19.0 11.0 19.2 13.6 17.0 18.2 18.6 10.5 24.2 13.2 16.5 27.2 18.2 10.0 30.3 12.7 16.0 40.2 17.8 9.5 37.8 12.3 15.5 52.4 17.4 9.0 45.5 11.8 15.0 71.0 17.0 8.5 55.2 11.4 14.5 94.2 16.6 8.0 67.8 10.9 14.0 128.2 16.2 7.5 89.5 10.5 13.5 186 15.8 7.0 169 10.0 13.0 360 15.3 6.9 480 9.9 12.8 570 15.2
Oxygen Not measured Reaction mixture le f t in Condens- reaction vessel for next ables Accumulated experiment. Trimethyl- borane Not measured (K-14 through K-16) Peroxide 0.24.67 mmoles (K-14 through K-16)
8 This corresponds to 10.0 mm. of carbon dioxide -236- TABLE E-10
DATA FOR EXPERIMENTS K-17-P AND K-18
Experiment K-17-P Experiment K-18 R Spherical 19.9°G. Spherical 19.9°C. I 247.7 255.8 F 203.8 210.2 d 1. 0670(27.0UC.) 1.0670(27.0°C.) 5.8 mm. 6.0 ram. PE02
k B CA B C (sec.) (mm. ) (s e c .) (mm. )
6.9 9.9 a 7.0 •• 10.0 13.2 2.8 15.4 14.0 1.8 16.2 11.5 14.5 14.0 12.5 9.8 14.9 10.5 25.4 13.2 11.5 16.6 14.0 10,0 34.A 12.7 11.0 21.3 13.6 9.5 46.5 12.3 10.5 26.4 13.2 9.0 63.2 11.8 10.0 33.2 12.7 8.5 91.0 11.4 9.5 40.8 12.3 8.1 176 11.0 8.5 64.3 11.4 8.0 660 10.9 8.0 86.2 10.9 7.5 119.0 10.5 7.0 240 10.0 7.0 360 10.0
Oxygen Not measured Reaction mixture le ft in C ondens- reaction vessel for next ables Accumulated experiment.
a This corresponds to 4-. 5 mm. of trimethyl- borane and 5.5 mm. of dimethylborylmethylperoxide. -2 37- TABLE E - ll
DATA FOR EXPERIMENTS K-18-P AND K-19
Experiment K -18-P Experiment K-19 E Spherical 19 .9°G. Spherical 19.9°G • I 242.7 243.3 F 201.6 203.0 d 1.0662(28. o°c.) 1.0654(29.0°C. ) Edo 5.4 mm. 5.2 mm. 2
A B C A BG (sec. ) (mm. ) (se c .) (mm. )
7.0 — 10. 0 8 1.8 5.2 13.0 2.9 15.3 7.0 — 10.0 ° 12.0 10.5 14.5 13.0 3.7 15.3 11.3 16.5 13.9 12.5 10.6 14.9 10.5 26.2 13.2 12.0 17.0 14.5 10.0 36.0 12.7 11.5 24.0 14.0 9.5 49.6 12.3 11.0 33.0 13.6 9.0 67.9 11.8 10.5 43.6 13.2 8.5 101.5 11.4 10. 0 54.9 12.7 8.3 148.2 11.2 9.5 71.8 12.3 8.2 360 11.1 9.0 91.9 11.8 8.5 121.0 11.4 8.0 169.0 10.9 7.5 250 10.5 7.0 570 10.0
Oxygen Not measured Oxygen Not measured C ondens- Condens- ables Accumulated ables A ccumula te d Trimethyl' borane Not measured (K-17-P and K-18-P) Peroxide 0.306 mmoles (K-17-P and K-18-P)
a This corresponds to 4.0 mm. of t rimethylborane and 6.0 mm. of dimethylborylmethylperoxide. b Added 4-.8 mm. of neopentane. -2 38- table E -12
DATA FOR EXPERIMENTS K-2 0 AND K-21
Experiment K-20 Experiment K-21 R Spherical 19.9°C. Spherical -20.1°C. I 308.2 241.8 F 268.3 147.2 d 1.0654(29.0°C.) 1.0670(27.0 C.)
?ROo2 e5.2 o mm. 12.3 mm.
A B C A B C (sec. ) (mm.) (sec.) (mm.)
1.9 5.3 1.8 5.2 13.0 15.3 a 11.1 4.0 Something 19.0 7.5 20.2 10.5 21.0 wrong-the 18.5 14.0 19.8 10.0 44.7 calculated 18. 0 20.5 19.4 9.5 59.6 in it ia l oxy- 17.5 28.0 19.0 9.0 161 gen pressure 17.0 35.5 18.6 8.7 660 is higher 16.C 54.8 17.8 8.6 960 than fin a l 15.5 66.8 17.4 pressure in 15.0 84.5 17.0 measuring 14.5 109.0 16.6 bulb. Also 14.0 147.8 16.2 there may be 13.5 220.4 15.8 an error on 13.2 330 15.5 the fir s t 13.0 910 15.3 four meter readings aft' the introduc' tion of the oxygen.
Oxygen Not measured Oxygen Not measured Condens- Trimethyl- ables Accumulated borane 0,000 mmole Trimethyl- Per oxide 0.085 mmoles borane Not measured (K-19 and K-20) Peroxide 0.1487 mmoles (K-19 and K-20)
a This corresponds to 10.0 mm. of neopentane. Meter reading 20 10 Fig. E-2. rndcr airto N. , eprtr -20,I°C. Temperature No. 2, Calibration Transducer rsue (mm.) Pressure !U ID 20 TABLE E-13
DATA FOE EXPERIMENTS K-22 AND K-23
Experiment K-220 Experiment K-23 R Spherical -20.1 C • Spherical -20.1 °G. I 24.3.0 251.1 F 216.2 237.0 d 1.0666(27.5°C.) 1.0658(28.5°C .) PR0 3.5 mm. 1.8 mm. 2
A B C A B C (sec.) (mm. ) (sec. ) (mm. )
1.9 5.1 2.0 5.1 5.6 5.1 8.5 4.0 5.4 7.0 5.0 19.8 7.9 3.8 23.6 6.8 -4.5 39.2 7.5 3.5 41.5 6.5 -4.0 65.5 7.0 3.0 115.5 6.0 3.5 108.0 6.5 2.5 274 5.6 3.0 181.4. 6.0 2.1 600 5.2 2.5 317 5.6 2.0 780 5.1 2.0 615 5.1 1.9 660 5.1
Oxygen Not measured Oxygen Not me a sure a Condens- C ondens- ables Accumulated ables Accumulated Trimethyl- borane Not measured (K-22 and K-23) Peroxide a 0.0668 mmoles (K-22 and K-23)
a Determined after 5 hours delay -241- TABLE E-14
DATA FOR EXPERIMENTS K-24 AND K-25
Experiment K-240 Experiment K-250 R Spherical -20.1 C. Spherical -20.1 C. I 282.8 317.4- F 261.1 298.7 d 1.0662(28.0°C.) 1.0658(28.5°C.) Pj>0 2.8 mm. 5.1 ram. 2
ABCAB C (sec.) (mm. ) (sec . ) (mm. )
2.0 — 5.1 2.0 0 5.1 5.0 2.0 7.9 7.3 3.7 10.0 4-. 5 16.2 7.5 6.5 12.1 9.3 4.0 4-2.4- 7.0 6.0 20.8 8.8 3.5 77.0 6.5 5.5 30.9 8.4 3.0 127.1 6.0 5.0 47.8 7.9 2.5 232 5.6 4.5 70.4 7.5 2.0 42 0 5.1 4.0 103.0 7.0 1.8 750 4.9 3.5 154.2 6.5 3.0 233 6.0 2.3 407 5.4 2.0 630 5.1
Oxygen Not measured Oxygen Not measured Condens- ables Accumula ted Condens- ables Accumulated -242- TABLE E-15
DATA FOR EXPERIMENTS K-26 AND K-27
Experiment K-26 Experiment K-27 R Spherical -20.1°G • Spherical -20.1°C • I 350.1 364.0 F 309.1 318.7 d 1.0658(28.5°C.) 1.0681(26.0°D.) Prq 5.4- mm. 6.0 mm. 2
AB CA BC (sec.) (mm. ) (sec.) (mm. )
4.4 7.4 3.6 — 6.6 10.3 3.1 12.5 10.0 4.2 12.2 9.5 9.3 11.8 9.0 11.6 11.4 9.0 14.2 11.4 8.5 16.5 11.0 8.5 20.9 11.0 8.0 22.9 10.5 8.0 29.1 10.5 7.5 31.1 10.1 7.5 41.1 10.1 7.0 43.0 9.7 7.0 57.2 9.7 6.5 58.0 9.3 6.5 80.7 9.3 6.0 80.8 8.8 6.0 115 8.8 5.5 110.0 8.4 5.5 163 8.4 5.0 158.3 7.9 5.0 257 7.9 4.5 215 7.5 4.3 510 7.3 4.0 329 7.0 4.3 600 7.3 3.6 540 6.6 3.3 690 6.3 3.2 780 6.2 3.1 840 6.1 3.1 960 6.1
Iff m/!kn 0 ^ A v ai v v tug a u uj . c u Oxygen Not measured Condens- Condens - ables Accumulated ables Accumula ted Trimethyl- borane Not measured (K-24 through K-26) Peroxide 0.1810 mmoles (K-24 through K-26) -2 4 3 -
TABLE B -1 6
D AT A FOR EXPERIMENTS K-28 A LID K-29
Experiment K-28 Experiment K-29 L. Spherical -2 0.1°c. Spherical -20.1°C . I 38 3. 2 385.2 321.6 F 298. 4 d 1 . 0681(26.0 C • 1.0681(26.0 C .) ^RQ 11 • 2 mm. 8 .4 mm. 2
AB G ti Jd G (sec. ) (mm. j (sec. ) (mm. )
3.5 — 6.5 2.0 5.1 16.0 3.4 17.2 12 .0 13.9 a 13.0 11.5 14 • 7 22.0 5.5 22.1 11.5 21.0 13.5 21.0 11.4 21.3 10.5 31.0 12.6 20.0 20.2 20.5 10.0 40.3 12 .2 19.0 31.0 19.7 9.5 51.0 11.8 18.0 48.2 18.9 9.0 67.4 11.4 17.5 60.5 18.5 8.5 94.7 11. 0 17.0 76.8 18.0 8.0 152.0 10.5 16.5 99.5 17.6 7.8 240 10.4 16.0 13 0.1 17.2 7.7 390 10.3 15.5 182.4 16.8 7.5 600 10.1 15.0 305 16.3 7,4 750 10.0 15.0 390 16.3 7.3 900 10.0 14.9 690 16.3
Oxygen Not measured Oxygen Not measured G ondens- C ondens- ables Accumulated ables Accumulated Trimethyl- ’oorane Not measured (K-27 through K-2 9 ) Peroxide 0.3034 mmoles (K-2 7 through K-29)
g This corresponds to 8.8 mm. of neopentane. -2 44-
table 13-17
D&Ta FOE EXPERIMENTS K-30 khD K-30-P
Expe riment K-30 Experiment K-30-F R Spherical -2 0.1°C. Spherical -20.1°G. I 321.6 266.1 F 266.1 218.2 d 1.0681(26.0°C . ) 1.0675(26.5°G.) 6.3 mm. PE0 7.3 mm. 2
a B C a BC (sec.) (mm. ) (sec.) (mm. )
3.6 11.1 7.5 10.0 17.0 3.6 18 .0 14.5 4.3 15.9 15.0 10.6 16.3 14.0 9.3 15.5 14.0 17.0 15.5 13.5 14.5 15.1 13.0 26.0 14.7 13.0 22.6 14.7 12 .0 4 0 . 8 13.9 12.5 31.3 14.3 11.5 51.2 13.5 12.0 43.2 13.9 11.0 65.5 13.0 11.5 56.8 13.5 10.5 81.9 12.6 11.0 76.1 13.0 10.0 107.9 12.2 10. 5 98.6 12.6 9.5 143.4 11.8 10.0 144.6 12 .2 9.0 205 11.4 9.5 211 11. 8 8.5 300 11.0 9.2 360 11.6 3.1 480 10.6 9.1 600 11.5 ' 8.0 72 0 10.5 9.0 72 0 11.4 7.5 1950 10.1
Reaction mixture left in Oxygen Not measured reaction vessel for next Condens- experiment. ables - infrared spectrum agrees with dimethyl- borylmethy1pe roxide Peroxide 0.1759 mmoles (after infrared spec trum) Meter reading 5 0 5 20 15 10 5 0 i. 3 Tasue Clbain o 3 Tmeaue I9.9°C. Temperature No. 3, Calibration Transducer -3. E Fig. - 2 . 45 rsue (mm.) Pressure - —246 — TABLE E-lS
DATA FOE Ea EEKIMEBTS K-31 AND K-32
Experiment K-31 Experi ment K-32
E Spherical 19.9°C. Spherical 19.9 C • I 290.3 288.9
F 249.9 255.1 A d 1 .O645(30.CC= .) 1 . 0636(31.0 G. ) PR0 5.3 mm. 4.4 mm. 2
&BC AB c (sec.) (mm. ) (sec. ) (mm. )
4.9 — 5.2 16.2 15.0 15.1 - ' 14. o a 22.0 2.0 19.7 21.5 6.5 19.3 21.0 8.4 18.9 21.0 13.1 18.9 20.0 16.6 18.1 20.5 20.4 18*5 19.0 26.0 17.3 20.0 27.9 18.1 18.5 33.2 16.9 19.5 34.2 17.7 18.0 40.3 16.5 18.5 45.8 16.9 17.5 50.0 16.0 18.0 52.7 16.5 17.0 69.2 15.6 17.0 66.6 15.6 16.5 112.4 15.2 16.5 83.0 15.2 16.2 240 15.0 16.0 12 5.1 14.8 16.2 480 15.0 15.5 2 02 14.4 15.2 300 14.1 15.1 510 14.0 15.1 72 0 14.O
Oxygen 0.0013 mmoles Oxygen ^ 0.00078 mmoles G ondens- C ondens- ables added to pyridine ables added to pyridine (see Appendix F.) (see Appendix F.)
a Thi3 corresponds to 8.8 mm. of 'neopentane. b Gas phase chromatography indicated methane present in trace amount. 0 5 10 15 20 Pressure (mm.)
Fig. E - 4. Transducer Calibration No. 4, Temperature -20.I°G -248- TABLE E-19
DATA, FOK EXPERIMENTS K-33 AND K-34
Experiment K—33 Experiment K-34 R Spherical 19.9°C • Spherical --20.1oC • I 191.0 230.2 F 160.5 176.2 d 1.0658(28.5°C. ) 1.0645(30.0UC.) Pvx o 4 • 0 mm. 7.0 mm. 2
A B CA B G (sec. (mm. ) (sec. ) (mm. ) 8.5 8.4 6.7 — 6.7 13.0 3.3 12.3 14.5 3.3 13.4 12.5 9.9 11.9 13.0 11.5 12 .2 12.0 17.3 11.5 12 .0 20.3 11.3 11.0 38.0 10.6 11.0 34.6 10.5 10.5 50.1 10.2 10.5 44 • 0 10.0 10.0 71.5 9.8 10.0 57.6 9.6 9.5 97.8 9.3 9.5 74.9 9.2 9.0 143.1 8.9 9.0 95.6 8.7 8.7 240 8.6 8.5 123.8 8.3 8.5 330 8.4 8.0 166 7.9 8.5 510 8.4 7.5 232 7.4 8.4 720 8.4 7.0 515 7.0 6.4' 526 6.4 6.2 72 0 6.3 6;i 900 6.2
Reaction mixture le f t in Oxygen Not measured reaction vessel and bath tem- Condensables - Special perature lowered to -20.1°C. treatment At this temperature the meter (see; Appendix F.) reading was 0.71 and corresponded to a pressure of 7.1 mm. (From ideal gas law, calculated pressure was 7.2 mm. ) Oxygen Not measured Trimethyl- borane Hot measured Peroxide 0.0445 mmoles (after 24 hours delay) Meter reading x 10 20 25 10 15 Fig. E - 5 E - Fig. rndcr airto N. , eprtr I9.9°C. Temperature 5, No. Calibration Transducer „ 2
9 — rsue (mm.) Pressure -2 50-
TABLE E-20
DATA FOR EXPERIMENTS K-35 AND K-36
Experiment K-35 Experiment K-36 R Spherical -20.1°C. Snherical 19.9°C. I 294.1 172.2 F 232.0 145.9 d 1.0645(30.0°C.) 1.0675(26.5°C.) PftQ S . 1 mm. 3.4 mm.
ABC AB C (sec. ) (mm. ) (sec, ) (mm. )
10.3 9.9 7. 8 8.0 20.0 3.5 17.7 11.0 10.5 10.8 17.0 11.5 15.3 10.5 21.0 10.4 16.0 17.0 14.6 10.0 35.5 10.0 15.0 25.0 13.8 9.5 53.3 9.5 14.0 40.0 13.0 9.0 77.7 9.1 13.0 63.0 12.2 8.5 112.8 8.6 12.5 79.7 11.8 8.0 198 8.2 12.0 105.0 11.3 7.8 480 8.0 11.5 142.1 10.9 7.8 780 8.0 11.0 193 10.5 7.8 900 8.0 10.0 354 9.6 9.5 560 9.2 9.2 905 8.9
Oxygen a 0.0012 mmoles Oxygen O.OOO46 mmol< Cg fraction, 0.0005 mmoles Trime thyl- Trimethyl borane 0.0595 mmolei mm a a ■D*». - .-i J « A a 1 r a borane 0.0040 WiU W W W iOJ.UAJ.UO U*U^Lp^ Peroxide 0.1018 mmoles , (mass spectrum obtained) Residue(see Appendix F.)
s Contained trace of methane, b Mass spectrum indicated trimethylborane present. -2 51-
- TABLE E-21
DATA FOR EXPERIMENTS K-37 AND K-38
Experiment K-37 Experiment K-3S E Spherical 19.9°C. Spherical 19.9°C. I 298.5 195.0 F 260.0 153.1 d 1.0670(27.0°C .) 1.0681(26.0°G.) PR02 5.1 mm. 5.4 mm.
AB C A B G (sec.) (mm.) (sec. ) (mm.)
4.5 mm 5.0 5.5 5.9 15.8 - 15.0 a 11.5 2.4 11.3 21.5 8.6 19.6 11.0 7.8 10.8 21.0 16.8 19.2 10.5 12.9 10.4 20.0 35.4 18.4 10.0 19.6 10.0 19.5 46.3 18.0 9.5 27.7 9.5 19.0 55.3 17.6 9.0 37.4 9.1 18.5 70.0 17.2 8.5 50.6 8.6 18.0 86.7 16.8 8.0 65.6 8.2 17.5 111.3 16.4 7.5 88.5 7.7 17.0 148.3 15.9 7.0 121.0 7.3 16,5 222 15.5 6.5 - c 6.8 16.2 300 15.3 5.7 >390 6.1 16.0 461 15.1 5.5 >600 5.9 15.9 600 15.0 5.4 >840 5.8 15.8 1140 15.0.
Oxygen ^ 0.0014 mmole s Oxygen 0.00063 mmole! Pr opylene 0.1592 mmoles Trimethyl - Trimethyl - borane 0.00934 mmolei borane - Not separated Peroxide 0.0829 mmoles from propylene Peroxide 0.0692 mmoles (after mass spectrum)
a33his corresponds to 10.0 mm. of propylene. ^Contains a trace of methane. cWatch accidentally stopped, and started again. Meter reading 2.0 30 4.0 5.0 0 i . -. rndcr airto N. , eprtr I9C (cl: 10 * (Scale: Ivolt) I99°C. Temperature No. 6, Calibration Transducer Fig. E-6. 10 - 252 rsue (mm.') Pressure 20 " 30 40 Meter reading 25 20 10 i. -. rndcr airto N.7 Tmeaue I9.9°C. Temperature No.7, Calibration Transducer E-7. Fig. 1 1 20 15 10 5 -253- rsue (mm.) Pressure -2 54- TABLE E-22
DATA FOR EXPERIMENTS K-39 AND K-40
Experiment K-39 Experiment K-40 B Spherical 19.9°C. Cylindrical Doughnut 19.9°' I 593.1 292.4 F 549.5 225.0 d 1.0688(25.0°c.) 1.0635(31.0°C.) Fp n 5.9 mm. 10.2 mm. 2
Aa B CA B C (sec. ) (mm.) (sec.) (mm.)
—» .45 b 5*° e 7.5 7.5 3.88 - 36.3 C 18.0 3.7 16.6 4.60 2.3 42.0 15.0 11.9 14.1 4.50 27.1 41.2 13.5 19.7 12.8 4.40 39.5 40 • 4 12.5 29.6 11.9 4.30 55.8 39.6 12.0 39.4 11.5 4.20 73.8 38.8 11.0 69.0 10.6 4.10 116.1 33.1 10.5 103.6 10.2 4.02 210 37.4 10.3 181 10.0 4.01 304 37.3 10.3 270 10.0 4.01 72 0 37.3 10.3 540 10.0
Oxygen . 0.0150 mmoles Oxygen S 0.0369 mmolei Propylene 0.500 mmoles C2 Fraction 0.000032 " Trimethyl- Trimethyl borane (if any) borane 0.000024 " not separated from Per oxide 0.0973 propylene Fraction® 0.00205 mmoles Peroxide 0.0708 mmoles (after mass spectrum *)
aActual meter reading, measured on 10 = 1.0 volt scale. This reading on 3.0 = 0.3 volt scale. cGorrespnnds to 31.3 mm. of propylene. ^Mass spectrum agreed with that for original propylene. eMass spectrum obtained (see Appendix F .). ^Agree with that for dimethylborylmethylperoxide. ^Contained trace of methane. -255-
TABLE E-2 3
DATA FOR EXPERIMENTS K-41 AND K-42
Experiment K-41 Experiment K-42 R Cylindrical Doughnut Cylindrical Doughnut 19.9°C. 19.9°C. I 234.1 190.9 F 185.6 157.7 d 1.0688(25.0°C.) 1.0684(25.5 C.) PR0 mI!1» 5.0 mm. 2
AB C A B C (s e c .) (mm.) (sec.) (mm. )
7.5 — 7.5 7.5 7.5 15.0 3.6 14.1 13.0 1.7 12.4 13.0 11.6 12.3 12.0 11.4 11.5 11.5 18.1 11.0 11.5 18.6 11.0 11.0 22.7 10.6 11.0 27.2 10.6 10.0 33.2 9.7 10.5 36.1 10.2 9.5 43.8 9.3 10.0 50.5 9.7 9.0 6O.4 8.9 9.5 66.0 9.3 8.5 90.1 8.4 9.0 90.1 8.9 8.1 178.4 8.1 8.5 185.1 8.4 8.0 180 8.0 7.7 300 7.7 7.8 270 7.8 7.5 570 7.5 7.7 360 7.7 7.5 840 7.5 7.5 1050 7.5 n
Oxygen Not measured Oxygen Not measured C end 9*1®** C ondenS' able s Accumulated ables Accumulated -256-
TABLE E-24
DATA FOR EXPERIMENTS K-43 AND K-44
Experiment K-43 Experiment K-44 R Cylindrical Doughnut Cylindrical Doughnut 19.9°C. 19.9°0. I 162.0 242.2 F 127.3 180.4 d 1.0675(26.5°C.) 1.0670(27.000.) PR 0 ^ * 2 mifl * 9.3 mm.
A B C A B C (s e c .) (mm.) (sec.) (mm. )
4.7 _ 5.0 4.7 5.0 10.0 4.6 9.7 14.0 4.6 13.2 9.5 11.4 9.3 13.0 10.5 12.4 9.0 20.6 8.9 12.0 19.2 11.5 8.5 31.4 8.4 11.5 25.6 11.0 7.5 65.4 7.5 10.5 44.8 10.2 7.0 91.6 7.1 10.0 66.0 9.7 6.5 125.6 6.6 9.7 229 9.5 6.0 189.0 6.2 9.5 283 9.3 5.5 277 5.7 9.4 510 9,2 5.1 570 5.4 9.4 600 9.2 5,0 630 5.3 5.0 690 5.3
Oxygen Not measured Oxygen Not measured C ondens- G ondens- ables Accumulated ables Accumulated C2 frac tion 8 0.00024 mmoles (K-41 through K-44) Trimethyl- borane 0.0293^ mmoles (K-41 through K-44) Peroxide 0.2829 mmoles (K-41 through K-44)
8 Gas phase chromatography indicated ethane present, 0 This value may be low because of incomplete separation. o Meter reading X 20 25 10 i. -. rndcr airto N. , eprtr -20.1°C. . 0 2 - Temperature 8, No. Calibration Transducer E-8. Fig. „ rsue (mm) Pressure 9 £• 10 n _ -253-
TABLE E-2 5
DAT/i FOB EXPERIMENTS K-45 AND K-46
Experiment K-45 Experiment K-46 R Cylindrical Doughnut Cylindrical Doughnut -20,1°C. -2 0 .1°C. I 157.3 200.5 F 131.2 159.9 . d 1.0696(24.0°C.) 1.0645(30.0 C.) Pr, r, 3.9 mm. 6.1 ram.
AB C AB C (sec.) (mra. ) (s e c .) (mm.) 6.6 — 6.4 6.7 - 6. 5 10.5 4*6 10.0 13.0 2.4 12.1 10.0 13.6 9.5 12 .0 10.6 11.2 9.5 26.5 9.1 11.5 16.0 10.8 9.0 46.8 8.6 11.0 23.7 10.4 3.5 71.4 8.2 10.5 33.7 10.0 8.0 117.4 7.7 10.0 43.5 9.5 7.5 202 7.3 9.5 67.4 9.1 7.0 340 6 .8 9.0 96.4 8.6 6.9 431 6.7 8*5 141.3 8.2 6.7 690 6.5 8.0 2 02 7.7 6.4 930 6.2 7.5 301 7.3 6.3 1170 6.2 7.0 518 6.8 6.3 1290 6.2 6.4 1110 6.2 6.3 1380 6.2 6.3 1620 6.2
Oxygen a 0.00036 mmoles Oxygen c 0.0011 mmoles Co Fraction 0.00020 mmoles C2 Fraction 0.00033 " Trimsthyl- 'i'rime thyl- borane 0.0413 mmoles borane 0.0141 mmoles Peroxide 0.0556 mmoles Peroxide O.O865 mmoles
E Analysis delayed 24 hours because of breakage to the vacuum system; however, trimethylborane and peroxide were fractionated and stored at -80° during the delay. Estimated as being 1/3 of to ta l from mixture; the rest was lo st because of breakage of the system. c Contains trace of methane. -2 59- TABLE E-26
DATA FOR EXPERIMENTS K-47 AND K-48
Experiment K-47 Experiment K-4& R Cylindrical Doughnut Cylindrical Doughnut -2 0 .1°C. -20.1°C. I 215.2 179.4 F 167.9 145.4 d 1.0658(28.5°C.) 1.0688(25.0°C.) pro2 7 *1 mm» 5.10 mm.
A B c AB C (sec.) (mm. ) (sec. ) (mm.) 6 . 6 - 6 .4 6.7 - 6.5 14.0 2.2 13.0 12.0 -L1 « Q/ 11.2 13.0 7.2 12.1 11.0 12 .2 10.4 12.0 17.2 11.2 10.5 19.0 10.0 11.5 22.9 10.8 10.0 31.0 9.5 11.0 32.5 10.4 9.5 46.2 9.1 10.5 43.0 10.0 9.0 73.6 8. 6 10.0 60.2 9.5 8.5 102 .2 8.2 9.5 83.2 9.1 8.0 161.1 7.7 9.0 118.2 8.6 7.5 247 7.3 8.5 164.8 8.2 7.0 436 6.8 8.0 231 7.7 6,8 630 6.6 7.5 362 7.3 6.5 960 6.3 7.0 600 6.8 6.3 1500 6.2 6.9 750 6.7 6.3 930 6 .6 6.7 1200 6.5 6.4 1500 6.2 6.4 1800 6.2
Oxygen 0.0054 mmoles Oxygen 0.00077 mmls. O2 Fraction 0.00007 " C2 Fraction 0.000094 " Trimethyl- Trimethyl- borane 0.00006 mmoles borane a 0.0277 mmoles Peroxide 0.0964 mmoles Peroxide b 0.0694 mmoles (after mass spectrum)
a Mass spectrum in agreement with that for tr i- methylborane. b Agrees with mass spectrum of dimethylborylmethyl- peroxide except that peaks at M/e = 56, 57, 72 and 73 seem slightly excessive. APPENDIX F
SPECIAL TREATMENT OF KINETIC
EXPERIMENT REACTION PRODUCTS
-2 6 0 - 261-
K-31 Condensables
The condensables of the final reaction mixture
from the reaction of 0.0812 mmoles of trimethylborane
with 0.0828 mmoles of oxygen in the presence of 0.137 mmoles of neopentane at 19.9°C. were condensed with
0.0810 mmoles of pyridine in a 50 cc. reaction bulb,
after allowing the mixture to react at room tempera
ture it was cooled to - 23°0 . and the volatile material
fractionated through traps at -138, -142 and -196°C.
The -196°C. trap yielded 0.0013 mmoles of material which
was shown to be a mixture of carbon dioxide and ethane
by gas phase chromatography. The material collected in
the -118 and -142°C„ traps was combined and an infrared
spectrum obtained. The infrared spectrum (Fig. F - l)
shows that this material is predominantly neopentane with a small amount of dimethylborylmethylperoxide
present. The pyridine reaction bulb now contained a white solid which was allowed to stand overnight at room temperature.
This white solid was believed to be the pyridine adduct of dimethylborylmethylperoxide previously reported by Petry (15). An infrared spectrum was taken of the vapor above the adduct and is shown in Figure F-2
This spectrum agreed with that which would be expected z o \ T f t A i* l Ifae Setu o te epnae rcin f K-31 of Fraction Neopentane the of Spectrum Infrared -l. F Fig* X X TRANSMISSION i, -, nrrd pcrm f h Vpr vr the over Vapor the of Spectrum Infrared F-2, Fig, j U S l
yiie dut f h Pout o K*~31. of Products the of Adduct Pyridine 263- -264- from a composite of the spectra of pyridine and methoxy- dimethylborane except for an extra band at approximately
5.8 micronsj this band is similar to that for formaldehyde.
A trace of hydroxydimethylborane may also be present.
The adduct was discarded. -265- K-32 Condensables
The condensables of the final reaction mixture of the reaction of 0.234 mmoles of trimethylborane with 0.0687 mmoles of oxygen a t 19.9°C. were condensed in a 50 cc. bulb with 0.230 mmoles of pyridine. The mixture was allow ed to warm to room temperature, then it was cooled with liquid nitrogen; and the heating-cooling cycle repeated.
Finally the mixture was cooled to -23°C. and the volatile material fractionated through traps at -118, -142 and
-196°C. From the -196° trap 0.001 mmoles of material were obtained. This was found (by gas phase chromato graphy) to be a mixture of carbon dioxide and ethane. kn infrared spectrum was obtained on the material collected in the -118 and - 142° traps; the spectrum which indicated a very small sample agrees with that for dimethylboryl- raethylperoxide. The pyridine reaction bulb which contained a white solid (combined pyridine adduct of unreacted t r i methylborane and dimethylborylmethylperoxide) was stored at dry ice temperature following the above mentioned fractionation. k sample of the vapor above the adduct at room temperature was obtained and the infrared spectrum obtained from this sample. The spectrum appeared to be a mixture of pyridine and dimethylborylmethylperoxide with a suggestion of the band at 5.8 microns noted in the spec trum obtained from the products of K-51. Once again a trace of hydroxydimethylborane may be present. The adduct was discarded. —266—
K-34 Condensables
The condensables of the final reaction mixture of the reaction of 0.1121 mmoles of trimethylborane and
0.1266 mmoles of oxygen at -20.1°C. were transferred into a tra n sfe r bulb. The mass spectrum of th is sample is
shown in Table F-l with that for dimethylborylmethyl- peroxide. Except for the peaks at M/e = 41 and 57 the spectra are in fair agreement. Whether these peaks in dicate the presence of other materials or merely changes
in cracking pattern caused by changes in instrument con ditions is not certain. The infrared spectrum of this
same sample was also in agreement with that for dimethyl-
borylmet hylperoxide .
After obtaining these spectra the sample was con densed in a 50 cc. bulb with 0,121 mmoles of pyridine and allowed to react at room temperature. The bulb was then cooled to -23°C„ and the volatile material collected in a trap cooled to -196°C. Only a small amount of material was collected and the infrared spectrum of it indicated that it was a mixture of the peroxide and py ridine. The infrared spectrum of the vapor over the adduct at room temperatures is given in Figure F-3. The spectrum shows the presence of pyridine, hydroxydimethyl- borane (dimethylbornous acid) and a carbonyl containing compound which most likely is formaldehyde. The adduct was discarded. -2 6 7 - TABLE F -l
MSS SPECTRUM OF K-34 COHDENSABLES
Relative Intensities M/e K-34 (ch3 )2bo2ch 3 AR.I.
10 0.4 0.3 0.1 11 2.2 1,8 0.4 12 1.0 0.5 0.5 13 2.0 1.7 0.3 14 3.8 3.3 0.5 15 100 100 16 3.5 2.5 1.0 17 0.5 0.6 -0.1 18 1.9 2.2 -0.3 24 0.9 0.8 0.1 25 2.6 2.3 0.3 26 7.0 5.5 1.5 27 10.3 8.4 1.9 28 20.6 17.0 3.6 29 27.2 28.1 -0.9 30 5.5 5.6 -0.1 31 6.2 6. 6 -0.4 32 2.1 2.2 -0.1 36 1.1 0.6 0.5 37 2.8 1.5 1.3 38 1.1 0.6 0.5 39 3.3 1.4 1.8 40 5.0 2.6 2.4 41 17.8 7.1 10.1 42 21.0 21.4 -0.4 43 64.1 66.7 -2.6 44 1.3 1.3 45 4.2 4.3 -0.1 50 0.9 - -0.9 52 0.8 0.7 0.1 53 1.6 1.4 0.2 54 1.1 0.5 0.6 55 3.8 3.5 0.3 56 18.2 14.6 3.6 57 67.5 53.6 13.6 58 2.5 2.4 0.1 59 3.5 4.1 -0.6 -268- TABLE F-l (continued)
Relative Intensities M/e K-34 (ch3)2bo 2ch3 ^ R .I .
72 9.3 7.4 0.9 73 32.8 30.3 2.5 74 - 0.7 -0.7 87 1.5 1.5 — 88 5.7 5.8 -0.1 109 0.2 - 0.2 110 0.9 0.8 0.1 111 1.2 1.1 0.1 jSK
BO !
Fig. F-3. Infrared Spectrum of the Vapor over the
Pyridine Adduct of the Products of K-34. -270- K-35 Residue o Since the reactions at -20.1 G. were characterized as having an excessive pressure decrease, it was believed that the explanation may be in the formation of a mater ial which was not very volatile at that temperature. In order to check this possibility the following was perform ed. kfter the final reaction mixture of K-35 was removed, the reaction vessel was closed and the temperature of the reaction bath raised to 19.9°C. (This temperature raising required 2 days because there were no heaters in the bath.) after the desired temperature was obtained the volatile m aterial present was removed. The sample obtained
(0.0017 mmoles) represented less than 1 per cent of the initial trimethylborane; however, a mass spectrum (Table
F-2) was obtained. This spectrum appears to be a mixture of methoxydimethylborane, dimethoxymethylborane and hydroxy- dimethylborane with some other materials also present.
Dimethylborylmethylperoxide may also be present, but true interpretation of this type of mass spectrum is very diffi cult. i'levertheless, the presence of these materials along with those given the higher (M/e) peaks does indicate that some compound(s) were left in the reactor at -20.1°G. -2 71- TABLE F-2
MASS SPECTRUM OF K-35 RESIDUE WITH POSSIBLE INTERPRETATION
Observed Estimated Peak Ht. Contribution M/e Peak Height MeB(0Me)2 Me2B0Me Me2BOH AP.H.
10 3.8 1.5 0.5 1.8 11 14.3 - 7.5 2.0 4.8 12 5.7 - 2.3 1.1 2.3 13 13.9 0.4 7.9 1.5 4.1 14 21.5 1.0 9.9 1.8 8.8 15 336.0 2 0.4 278.2 9.3 28.1 16 10.6 - 7.4 1.1 2.1 17 8.1 — — — 8.1 IS 29.5 - - 1.4 28.1 24 6.4 - 4.8 0.9 0.7 25 16.3 0.8 15.1 1.8 -1.4 26 36.4 1.8 30.0 2.8 1.8 27 50.0 2.3 41.4 3.8 2.5 28 147.9 4.8 44.9 8.3 92.4 29 216.2 6.9 79.7 8.4 121.2 30 95.2 0.9 3.0 - 93.1 31 52.2 3.6 8.9 — 39.7 32 26.3 1.3 - - 25.0 35 5.5 - - — 5.5 36 12.6 - 11.3 1.1 0.2 37 27.7 - 30.1 1.8 -4.2 38 10.8 - 11.3 0.8 -1.3 39 28.8 - 31.5 2.0 -4.7 40 22.9 0.7 19.8 4.3 -1.9 41 52.5 1.6 44.6 11.6 -5.3 42 83.0 8.6 30.5 46.8 -2.9 43 243.0 29.0 61.1 152.9 — 44 56.1 0.6 4.6 — 50.9 45 6.7 1.3 — — 5.4 47 6.0 -— — 6.0 52 5.0 -— 0.8 4.2 53 12.4 0.6 — 1.5 10.3 54 7.6 0.4 7.8 _ -0.6 55 26.8 2.8 28.3 — ^4.3 56 234.6 6.4 226.8 - 1.4 57 905.1 19.2 885.9 1.2 -1.2 58 26.7 1.0 19.1 2.1 6.5 59 24.9 2 . 1 2.1 20.7 71 3.7 — 1.2 2.5 72 26.7 21.4 2.8 2.5 73 86.8 86.8 — -272- TABLE F-2 (continued)
Estimated Peak Ht. Contribution Observed ------M/e Peak Height MeB(OMe)2 Me2BOMe He2 B0H AP.H.
( 81) 4. 7 —— 4.7 ( 83) 2.9 — — — 2.9 (100) 8.5 — — 8.5 (101) 31.7 - — _ 31.7 110 2.4 - — — 2.4 111 3.4 - — M 3.4 (119) 17.8 —— 17.8 (121) 17.3 — — — 17.3 (123) 5.6 - - - 5.6 -273- K-39 C. fraction 4 The reaction of 0.0781 mmoles of trimethylborane and 0.0921 mmoles of oxygen was carried out in the pre sence of 0.489 mmoles of propylene in hopes that the propylene would react with any methyl radicals that may be formed during the reaction. After the reaction was completed, the condensables were fractionated through traps and at -80, -118, -142 and -196°G. That which was collected in the -196° trap was identified to be propy lene from its mass spectrum. The material (0.002 mmoles) collected in the -142° trap should have contained any
^"hydrocarbons which might have been formed from the reaction of methyl radicals with propylene. The mass spectrum of this fraction is shown in Table F-3. This spectrum can be interpreted as being mostly methoxydi- methylborane with lesser amounts of dimethoxymethylborane, dimethylborylmethylperoxide and some unidentified sub- stance(s). One cannot completely rule out the possibility that the sample could have contained hydrocarbons.
Unfortunately the sample was too small for further in vestigation. The amount of material collected in the
-80° trap was nil. -274- TABLE F-3
MASS SPECTRUM OF K-39 FRACTION
WITH POSSIBLE INTERPRETATION
Observed Est. Peak Ht. Contribution by M/e Feak Height MeB(OMe)2 Me^BOMe Me?BOH /iP.H.
10 2.9 - 0.2 1.6 1.1 11 14.0 - 1.4 3.2 4.4 12 5.5 - 0.8 2.5 2.2 13 13.5 - 1.6 3.6 3.3 14 19.0 0.9 3.0 10.8 4.3 15 415.3 14.0 77.9 302.3 21.6 16 12.0 - 0.2 8.1 3.7 17 3.0 - 0.4 - 2.6 IS 11.1 — 1.5 — 9.6 24 6.3 - 0.7 5.2 0.4 25 19.4 0.4 1.9 16.4 0.7 26 36.3 1.1 4.2 32.6 -1.6 27 58.2 0.6 6.6 45.0 6.0 23 102.0 3.1 13.6 48.8 36.5 29 119.2 6. 0 23.0 86.6 3.6 30 14.0 - 4.2 3.3 6.5 31 61.7 2.2 5.0 9.6 44.9 32 39.3 0.9 1.6 — 36.8 36 12.0 — 0.6 12.2 0.8 37 30.8 - 1.3 32.7 3.2 38 14.5 ■ - 0.6 12.3 1.6 39 40.0 - 1.7 34.2 4.1 40 26.0 — 2.2 21.6 2.2 41 65.1 0.9 6.2 48.5 9.5 42 50.4 6.1 17.5 33.1 -6.3 43 117.0 19.0 49.7 66.4 18.1 44 4.9 0.2 1.0 5.0 -1.3 45 3.8 0.7 3.4 — -0.3 52 4.5 - 0.6 — 3.9 53 13.5 - 1.3 — 12.2 54 8.8 - 0.9 8.5 - 0.6 55 32.0 1.1 2.5 30.7 -2.3 56 261.5 3.8 11.7 246.4 -0.4 53 1014.0 10.4 41.0 962.6 — 58 23.5 0.4 1*8 2 0.8 0.5 59 10.5 0.9 2.8 2.3 4.5 71 4*7 —— 1.3 3.4 72 70.2 14.8 6.1 3.1 46.2 73 87.0 60.0 27.0 74 5.9 1.2 0.6 — 4.1 87 2.0 0.4 1.2 — 0.4 88 5.6 1.2 4.3 - 0.1 APPENDIX G
ESTIMATION OF FLAME TEMPERATURES
-275- -276-
In order to obtain some idea of the temperatures which might occur in the explosive oxidation of trimethyl- borane, flame temperatures have been estimated for three cases: (l) maximum temperature, (2) minimum temperature
and (3) probable temperature. For each of these cases the in it ia l amount of trimethylborane and oxygen used
in experiment EL 160 will b.e used.
Calculation of these temperatures will be made in the following manner. First a specific stoichiometry will be assumed for the overall reaction. Using standard
free energies of formation, the heat of reaction is cal
culated. Since the process is assumed to be adiabatic
then the heat of the reaction represents the amount of heat that must be absorbed by the products. The tempera ture change is then calculated by the equation
“^rea ctio n - °PT where op represents the total heat capacity at constant pressure of all the products. Although the actual process was at constant volume, the use of Cp’s rather than C^*s does not greatly affect the results.
Case 1. Maximum Temperature
Reaction assumed (amounts in mmoles):
0.113 B(CH3)3(g) + 0.223 ^ 2 ^ ) — ^ 0.024.8 B203 (g l.)
+ 0.1487 C0(g) + 0.223 H20(g) + 0.0634 B(CH3)3(g) TABLE G-l
THERMODYNAMIC DATA. FOR MAXIMUM FLAME TEMPERATURE
Amount ^ H°f298.l6 a AHf CP ave b CP x 103 Substance (mmoles) (kcal/mole) (cal) (cal/mole-degree) (cal/degree)
0 . 024.8 -300.97 -7.46 27.3 c 0.68 B2°3 (gl) CO(g) 0.1487 - 26.42 -3.93 7.6 1.13
H20(g) 0.2230 - 57.80 -12.89 9.3 2.07 -277- B(CH3)3 (g) 0.0634 - 29.8 -1.89 41.9 2 .40
B(CH3)3 (g) 0.113 - 26.17 -3.37 - -
°2 (s) 0.223 0 0 -—
Q Values obtained froia Rational Bureau of Standards circular "Selected Values of Chemical Thermodynamics Properties - Series III." B Average value for temperature range 300-1300°K. Obtained from data In the source given in footnote a. c became liquid at 723°C. and 1 atmosphere pressure. -278- From the data given in Table G-l the following nay
be obtained:
AH1 = AHf products “ Hf reactants = -2o*17 " (-3.37) = -22.8 cal.
(At )., = = 3,630°G. - cPt 6.2 8 x 10“3
The Maximum Flame Temperature is approximately 3,650°C.
It should be kept in mind that this represents the
maximum flame temperature for those oxidations in which
no carbon dioxide is formed (i.e., those reactions with
a mole fraction of oxygen below 0.7.) For those reactions
in which carbon dioxide is formed, much higher tempera
tures are to be expected.
Case 2. Minimum Flame Temperature reaction assumed (amount in mmoles):
0.113 BMe3(g) + 0.223 02 (g) — ^ 0.02*8 B203 (gl.)
+ 0.223 H20 (g) + 0.0634 B(g ) + 0. 1902 0 (g)
+ 0.2853 H2(g).
From the data given in Table G-2 the following may be obtained:
AH2 =AHf products ”^ f reactants ~ - (-3.37) » 20.51 cal.
& t ) 2 = 1 ^ 5 ^ = ______= - 3 , 2 oo°c. cPl 6.41 x 10“3
This result yields a minimum temperature below absolute zero. Although this is a ridiculous temperature it does TABLE G-2
THERMODYNAMIC DATA FOR MINIMUM FLAM TEMFEliATUKE
AHf Cp L Amount AH°F298.16 a GP x 103 Substance (mmoles) (kcal/mole) (cal. ) (cal/mole-degree) (cal/degree)
B203 (gl) 0.024.8 -300.97 -7.46 14.7 0.36 co(g ) 0.1487 - 26.42 -3.93 6 .96 1.03
H20(g) 0.2230 - 57.80 - 12.89 8.03 1.79
B (g ) 0.0634 138.16 8.76 4.97 0.32
C(g) 0.1902 171.70 32.66 4.97 0.94
H2(g) 0.2853 0 0 6.90 1.97 b(ch3)3 0.113 - 29.8 -3.37 - —
°2 (g) 0.223 0 0 - -
a Values obtained from National Bureau of Standards circular "Selected Values of Chemical Thermodynamic Properties - Series III." b Values at 298.16°K. obtained f rom source given in footnote a. -280-
show that induced decomposition of the excess trimethyl- borane can result in lower flame temperatures. Similarly, any reaction which leaves free atoms or free radicals as products w ill evolve less heat, and lower the flame tem perature .
Case 3. Probable Flame Temperature
Keaction assumed (amounts in mmoles):
0.113 BMe3(g) + 0.22602 (g) ----> 0.339 C0(g) + 0.113 30(g)
+ 0.508 H2(g)
From the data given in Table G-3 the following may
be obtained:
£H3 = -10.4.0 - (-3.37) = -7.03 cal. 7.0 3 (At), = ------— _ = 86o°c. 3 8.17 X 10-3
The probable flame temperature is therefore approximatelyy
880°G. Again i t should be kept in mind that this is a probable flame temperature for this particular mixture.
In regard to the assumed reaction it is of interest to compare the products with those actually obtained from
EL 160. Thus for carbon dioxide 0.339 mmoles are assumed and 0.298 mmoles were obtained, for hydrogen 0.508 mmoles assumed and 0.378 mmoles obtained. There is l i t t l e in formation regarding boron compounds in the analyses. In view of the fact that peaks for water appeared in the mass spectrum of fraction E of EL 160, i t would appear TABLE G-3
THERMODYNAMIC DATA FOR PROBABLE FLAME TEMPERATURE - ..... o" — ..... — i\Hf Amount f 298.16 a Cp ave ^ c^ x 10^ Substance (mmoles) (kcal/mole) (c a l) (cal/mole-degree (cal/degree)
C0(g) 0.339 -26.42 - 8.96 7.6 2.58
BO (g ) 0.113 -12.75 — 1.44 7.7 0.87
H2(g) 0.508 0 0 9.3 4.72
B(CH3)3(g) 0.113 -29.8 - 3.37 --
°2 (g) 0.226 0 0 - -
a Values obtained from National Bureau of Standards circular "Selected Values of Chemical Thermodynamic Properties - Series III." b Average value for temperature range 300-1300°K. Obtained from data in the source given in footnote a. -282- that the low yield of hydrogen is partially due to water formation. Whether this water formation will lead to higher temperatures or not will depend on the state in which boron is considered to be. It is obvious that if much water is formed, there w ill not be enough oxygen available for the formation of monoboron monoxide.
In general it appears that the explosive oxidation of trimethylborane - oxygen mixtures which do not have sufficient oxygen for complete oxidation may be regarded as two processes - one an oxidation, the other an induced decomposition. Thus as the oxygen is increased the de composition mode of reaction should become less important, and'.the resulting flame temperature greater. Just how low a temperature is to be oxpected for mixtures rich in trimethylborane is unknown; however for oxygen rich mixtures, temperatures in the neighborhood of 4000°C. may be expected. AUTOBIOGRAPHY
I, James Edward Coleman, was born in Newport,
Arkansas, on October 6, 1928. I received ray secondary education in the public schools of El Dorado, Arkansas, and ray undergraduate training at Louisiana State Uni versity which granted me the degree of Bachelor of
Science in Chemistry in June of 1950. I remained at
Louisiana State University until August of 1952 at which time I received the degree of Master of Science.
During the period as a graduate student at Louisiana
State University I served as a Laboratory Assistant in the laboratories of Qualitative, Quantitative and
Instrumental Analysis and investigated a problem in the field of Infrared Spectroscopy under the direction of Dr. George L. Cunningham. In September 1952 I entered
The Ohio State University where I specialized in Kinetics and Boron Chemistry under Professor Frank Verhoek. Dur ing the period September, 1952,to March 1958 I held several research assistantships. For the spring quarter of 1958, I was the recipient of a fellowship from the
Du Pont Research Fund,,
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