THE SOLUBILITY OF DOTRIAOONTANE AND TETRACOSANE IN CIS AND TRANS DECAHYDRONAPHTHALENE

"by

Sun Wing Tip

A Thesis submitted in Partial Fulfilment of The Requirements for the Degree of

MASTER OF APPLIED SCIENCE

in the Department of

CHEMISTRY

The University of British Columbia April, 1941. ACKPTOWLEDGEMMT

The writer wishes to express Ms appreciation and thanks to Dr. W. P. Seyer for his valuable and helpful suggestions given to him throughout this research. CONTENTS

Page X xntro due t ion • &«««.•»•« *•»*•*••••«•• 1 II Materials used and Its Preparation »«»»»*»«•»»•» 4 2. • 0xs Decalxn «.«.«•«•.•••..••«...»•«»«»»..» 4 2• Dotrxacontane »•»».««•«.»«««»«*.«•«««««««. 5 3. Determination of Melting Point ...... 7 III Apparatus used and Experimental Procedure ...... 9 1« Capillary Method ...... 9 2* 33\il"b l^Eetlxod. 10

IV Resixlt s •«*••»•»*•«»••»*• «*«»«a»»»»oft»*ft»*& 12 ¥ Treatment of Results ...... • 17 71 Conclusion ...... 19 Sifrlio^rapii^r • «*•••• & «®*©6«©«*«*»«a&*»» SO j^ia^rams •«••*«••«• © • • *«• «.«*«&©•*» Melting Point Apparatus ...... 7a Graphs 1. Weight percent Dicetyl vs. Temperature ... 2. Mol percent Dicetyl vs. Temperature ...... 3. Mol percent Dicetyl in various solvents vs« Temperature ...*«••.»*«•»...... 4. Log Mol fraction Dicetyl vs. Reciprocal of Temperature The Solubility of Dotriaoontane in Cis Decalin

I Introduction A considerable amount of information regarding the mutual solubilities of are available in the literature. About thirty years ago Holde found that light hydrocarbons when added to petroleum caused the asphalt • • 1 portion to be precipitated. In 1932 Pilat and Godlewicz g extended this idea and repeating the work of Kling treated a Polish petroleum with and precipitated most of the asphalt in the crude. The remainder of the asphalt was precipitated by using at a pressure of 30 atmospheres. This work established the fact that mutual solubility of hydrocarbons was governed largely by the molecular weights of solute and solvent. These facts are very valuable to the oil companies and already extensive use has been made by them in isolating and purifying certain petroleum fractions by utilizing solvents of various selective powers. In spite of all this information. , very little was still known of the quantitative, nature concerning the mutual solubilities of hydrocarbons* 3 In 1936 Dr. Seyer and Fordyce initiated the study of the systems of dicetyl and and dicetyl and propane to provide quantitative data on the mutual solubilities of hydrocarbons. They found that the mutual solubility : of hydrocarbons is a function of their molecular weights* Also from their curves of concentrations in mole percent against the freezing point temperatures they found that in the neighborhood of 55°G there is a change in the curvature of the curve. From this point downward solubility changes rapidly with the temperature, indicating the occurrence of two forms of dicetyl* Evidence for the existence of two forms of dicetyl was later found by measuring the refractive index at various temperatures below its melting point. The transition point is about 55°C.

The following year Dr. Seyer4 extended this investigation by obtaining freezing point data of six separate systems of dicetyl with some low molecular weight hydrocarbons. The hydrocarbons used were as follows: , , , , cyclohexane and benzene. From the curves of mole concentration against temperature for each system, there is a tendency for all the curves to coincide from the melting point of dicetyl on, until the concentration of this substance falls to about 40 mole percent, then the solute appears to exert its influence in determining the shape of the freezing point curve. These systems also showed no eutectic point or, if such a point exists, it would lie very close to the freezing point of the solvent. Since the study of decahydronaphthalene or decalin is of great theoretical interest mainly because of its two isomers trans and cis, it is intended to determine in this research the mutual solubility of dicetyl in cis decalin. The primary object is to find whether a saturated dicylic ring compound would have any serious affect on the solubility of dioetyl, secondly, to see whether or not a eutectic point is formed. Cis decalin was used because of its abnormal behavior as determined from the various physical properties such as viscosity, vapour pressure and refractive index measurements, whereas the trans decalin behaves quite regularly. Further it is hoped that the data obtained may 5 be used to check the equation of HiIdebrand . II Materials used and Its Preparation 1. Decalin The deoalin was brought from Eastman Kodak Company which was about 50 percent trans. The composition of the crude decalin is found to vary. These variations are probably due to variations in the hydrogenation process by which the decalin is manufactured. The cis decalin was separated from the trans by vacuum distillation at a pressure of 8 mm. of Hg. A charge of about 2000 cc. of the crude decalin was introduced in the still. The trans having a lower boiling point comes off in the first fractions. The refractive index of the various fractions were taken and those which contain high cis were mixed together and the whole rerun for pure cis. For further details and description of the distillation apparatus refer to the following theses: '

Kirk BASc Thesis 1935 Walker MASe Thesis 1937 Davenport MASc Thesis 1939 Then the high cis fractions are recrystallized for pure cis. This is done in a partially-evacuated double-wall glass flask, using a platinum resistance thermometer. By cooling a mixture high in cis, solid cis is formed leaving the mother liquid relatively higher in trans, this is of course assuming a binary system where there is a eutectic point. The liquid is poured off leaving pure cis with entrained trans. This procedure was repeated until the 5

temperature of cis formation remains constant for quite awhile. This temperature was considered as the freezing point of pure cis decalin. To avoid supercooling, the sample was innoculated with^frozen cis sample. The final freezing point of the cis decalin was taken as -43.22°C and was considered quite pure.

2. Dotriacontane or Dicetyl The normal straight chain dicetyl used in this work was synthesized from cetyl iodide by the method 6 of Sorabji . The cetyl iodide was prepared from CP. cetyl 7 alcohol according to the procedure of Krafft in which hydrogen iodide.was passed repeatedly into melted cetyl alcohol. The hydrogen iodide was prepared by the action of water on phosphorous tri-iodide, the latter formed from white phosphorous and crystals of iodine. The hydrogen iodide gas liberated was passed through a red phosphorous absorption tower to remove as much free iodine as possible and finally into liquid cetyl alcohol until the latter was completely saturated. The cetyl iodide is formed according to the reaction

c H + HI 0 H i6V i6W + 2° The cetyl alcohol was then purified to some extent by washing with distilled water repeatedly, using a fresh portion each time and separating after each washing in a separating funnel* The product was then reorystallized from ethyl alcohol removing the last traces of iodine. The cetyl iodide was then weighed and dissolved in ether and an excess amount of sodium^neeessary to remove the iodine was added. Since the procedure of Sorab-ji (loc. eit) was followed in this part of the synthesis, there is no need to repeat it here. The following reaction seems to take place:

2G16H33r -+ 23*a G32H66 + M

The crude dicetyl was purified by repeated crystal• lization from glacial acetic acid, followed by reerystallization from ether. For the final purification only glacial acetic was used. The bulk of the acid was removed by siphoning and the rest by filtering the crystals and acid through a Buchner funnel using suction. To remove the last trace of acid, distilled water was run repeatedly through the dicetyl crystals using fresh portions each time; about 5 liters in all were used. This removed all the acid, as water and glacial acetic acid are exceedingly soluble. Then the dicetyl crystals were dried in a vacuum desiccator for a few days, after which a melting point determination was made. The recrystallization was repeated until a constant melting point was obtained. Fifteen recrystallizations were made after the second melting point determinations and no increase in melting point of the product was noted; The dicetyl was considered pure. 7

3» Determination of Melting Point The melting point of a solid substance which does not sublime or decompose on heating to its melting point is one of the best criteria of purity. Hence this method was used to determine the purity of the dicetyl. The procedure 8 used follows that of Piper , the apparatus consisting of a o. glass bulb witluside arm,holding about 150-200 cc. of concentrated sulphuric acid. It is fitted with a glass tube with a calibrated thermometer graduated in 0.1°C inside it. The diagram in the next page is perhaps self explanatory. The bulb is not stirred and by using a small flame and regulating the rate of heating, it is possible with care to repeat the melting points within an accuracy of 0.1°C. The temperature at which the substance shows the first sign of melting is taken as the melting point of the dicetyi. The final melting point of the dicetyl was 69.55°C as measured by the calibrated mercury thermometer, including stem correction. This agrees with that of Piper's (loc. cit) value 69.5°C to 69.7°C, yet differing from the value of other 9 investigators. Hildebrand and Wachter pointed out that the melting point of dicetyl should be approximately 70°c and

they obtained a melting point of 70°C. If this is correct,

then the dicetyl must have contained some of the next lower hydrocarbon* ie. C„.,H- Since after fifteen crystallizations ox 64 the dicetyl showed no increase in the melting point, it was

considered pure.

8

- , It is interesting to note that the rate of heating affects the melting point as determined by this method. Time must be allowed for the transfer of heat through the wall of the capillary tube. Because the observations of thermometer and : sample are not simultaneous, the rate of heating must be slow enough to make the error from this source negligible. o o It • -is found that the rate of heating of 0.1 — ,0.2 per minute in the vicinity of the melting point gives very satisfactory results. 9

III, Apparatus used and Experimental Procedure 1. Capillary Method In determining the solubility of the system dicetyl and cis decalin by melting and freezing points, the capillary tube method \ is used. This method is by far the most common and convenient of all. It has the further advantage of requiring very small amounts of material. However, this is not by any means the best method to be used and great accuracy must not be expected, though extreme care was taken at all times during the readings. The apparatus consisted of a side arm flask previously described. Thin-walled capillaries about 1 mm. in diameter were made by heating and drawing out tubing that has previously been cleaned and dried. About 0.5 gm. of dicetyl was weighed out accurately in a "weighing bottle and enough cis decalin was added to give a one percent solution., The mixture was then heated until the whole melts and the solution was stirred and shaken to promote mixing. When complete mixing was assured, the liquid is introduced into weighed capillary tubes by capillary action and the content in the bottle was desixsated for weighing. Both the capillaries and the mixture in the bottle were weighed accurately to get the correct weight of the mixture. The weight of the hydrocarbon was taken .. to be constant, assuming, no evaporation, and by subtraction from the total weight, we get the weight of cis decalin added, from which the weight percent of dicetyl was 10

calculated. The length of the solid in the tube a/as about 2 mm. Then the tube was sealed and the mixture was shaken down to the end of the tube* The capillary tube <»as then immersed into the bath with the sample adjacent to the thermometer and the whole heated until melting occurred. The rate of heating was regulated so that the temperature rise MS less than 0.2° per minute in the vicinity of the melting point. The temperature where all the crystals disappear was noted. The bath was cooled until the white crystals of dicetyl appeared, upon which the bath was heated again slowly until the last trace of crystals in the tube just disappeared. The temperature at this point was taken as the freezing point of the mixture. The procedure was repeated with two other capillaries of the same mixture until the readings agreed with one another. The point of disappearance of the crystals was fairly sharp. More cis decalin was added and the procedure repeated as above.

2. Bulb Method o For temperature readings below 30 0 the bulb method was used. Thick-walled uniform bulbs of 2 cm. diameter were blown of pyrex glass tube and sealed to about 9 cm. stems of 3 mm. tubing. The dicetyl was weighed in a weighing bottle and cis decalin was added as before. After the mixing was complete, the solution was poured into the bulb previously cleaned by means of a fine-drawn glass funnel. The content in the bulb was frozen and the. end was sealed off. 11

For more, accurate determinations the frozen bulb should be evacuated so that, upon melting, the hydrocarbons would be under their own vapour pressure. The bulb was then placed in a water bath electrically heated and mechanically stirred. The freezing point was determined as before and appeared to be fairly sharp.

For readings between zero and 10°C, an acetone bath was used in a partially evacuated dewar flask. Dry ice was added to lower the temperature of the bath. Temperature readings were taken by a platinum resistance thermometer and no correction was needed. 12

IT Results

Table I.

Wt. of Wt. of . Wt. Percent Mol. Percent Freezing Pt.

Dicetyl Cis Decalin of Dicetyl of Dicetyl oc (gmsv)(-gmsv) " '

100.0 100.0 69.55 0.4301 0.0062 98.58 95.51 68.69 0.4286 0.0218 95.16 85.77 67.68 0.4276 0.0373 91.98 77.85 66.58 0.4266 0.0452 90.42 74.32 66.08 0.4256 0.0686 86.12 65.54 64.40 0.4246 0.1031 80.47 55.80 62.80 0.4252 0.1097 79.49 ' 54.25 62.41 0.4241 0.1419 74.93 47.82 61.06 0.4230 0.2565 62.25 33.58 56.68 0.4227 0.4207 50.12 52.21 0.4223 0.5850 41.92 18 »12 49.26 0.4209 0.9596 30.49 11» 8 5 44.05 0.4195 1.3196 24.12 8.83 41.20 0.4178 1.7050 19.68 6.98 39.21 0.0320 0.1497 17.61 6 • 15 38 . 52 0.4169 2.4231 14.68 5.01 36.80

0.4162 2.5860 13.86 4.70 36.16 13

gable I. (eont.)

Wt. Of Wt. of Wt. Percent Mol. Percent Freezing Pt. of Dicetyl of Dicetyl )ieetyl Cis Decalin, °C (gras*) .

0.4147 3.9917 9.41 3.08 32.95 0.3773 4.9830 7.04 2.26 30.55 0.0324 0*7201 . 4.31 1.36. 26.50 0.0306 0.8540 3.46 1.086 24.75 0,0141 0*5603 2.46 0.76 23.05 0.0119 0.7889 1.49 0.46 19.65 0.0104 1.0839 0.95 0.29 16.45 0.0161 3.0751 0.52 • 0.16 13.25 0.0112 11.3021 0.10 0*03 3.20 0.00 0.00 -41.22 Table II.,

Mol. Percent Freezing Pt. Log,JST 1 v in" of Dicetyl : °c 10 ^

100.0 69.55 95*51 68.69 1.98005 29.26 85.77 67.68 1.93334 29.35 77.85 66.58 1.89126 29.44 74.32 66.08 1.87111 29.49 65.54 64.40 1.81651 29.63 55.80 62.80 1.74663 29.77 54.25 62.41 1.73440 29*81 47.82 61.06 1.67961 29.93 33.58 56.68 1.52608 30.33 23.55 52.21 1.37199 30.74 18.12 49.26 1.25816 31.03 11.85 44.05 1.07372 31.36 8.83 41.20 0.94596 31.82 6.98 39.21 0.84386 32.02 6.15 38.52 0.78887 32.10 5.01 36.80 0.69984 32.27 4*70 36.16 0.67210 32.34 I 15

gable II.. (cont.)

Mol. Percent Freezing Pt. log,nlS 1 iU of Dicetyl oc «

3.08 32.95 0.48855 32.68 2.26 30.55 0.35411 32.94 1.36 26.50 0.13354 33.38 1.086 24.75 0.03583 33.58 0.76 23.05 -0.11919 33.77 0.46 19.65 -0.33724 34.17 0.29 16.45 -0.53760 34.54 0.16 13.25 -0.79588 34.93 0.03 3.20 -1.52288 36.20 0.00 -41.22 fable III.

ST Lf Tm (°abs.) T (°abs.) 0! (°C) ; .4.-575. - ... .

3873.7 342.55 1.0 342.55 69.55 0.9 341.20 68.20 0.8 339.67 66.67 0.7 337.93 64.93 0*6 335.97 62.97 0*5 333.67 60.67 0.4 330.91 57.91 0.3 327.42 54.42 0.2 322.61 49.61 0.1 314.72 41.72 0.05 307.22 34.22

If » 17.722 Kg Cal/mol. 17

V Treatment of Results The mole fraction of dicetyl was computed for each reading. From,-results, curves were plotted as shown in figure (1) and (2) respectively. Figure (1) showed the freezing point curve of dicetyl in cis decalin on.basis of weight percent dicetyl. The curve in figure (2) was plotted on^mole percent dicetyl basis. Also a plot was made of dicetyl in cyclohexane in figure (3), so as to compare with the dicetyl-cis decalin curve, the former results being taken from Dr. SeyerTs experimental data (loc. cit). It will be noted that the two curves almost run parallel from 0.5 N down. Since the two samples of dicetyl used were of slightly different melting point, it is rather hard to say whether the two transition points are the same or not.

The solubility data was also plotted with log-^ of mole fraction as ordinates and the reciprocal of the absolute temperature as abscissa in figure (4). Since the latent heat is a function of the temperature and assuming Raoult's law to hold over differential portions of the curves, it is possible to calculate the heats of fusion at different temperature. Hildebrand (loc. cit) derived the following equation for the solubility of solids.

log * = ~Lf (| ~ | ) (1) 4.575 m

where N - mole fraction of solute

s latent heat of fusion

Tm - melting point of dicetyl °K 18

• \ Garner proposed the following equation for the latent heat of fusion of the even paraffin hydrocarbons for the ex form: Q, x .6085n - 1.75 (2) where n = number of carbon atoms.

For dicetyl Q, = 17.722 Kg Cal/mol. By substituting this value into equation (1) and assigning different value for N, the corresponding values for T is calculated (Tablell.). The. curve of N versus T gave us the "Ideal Curve" as shown in graph 3. This was compared to the experimental curve. Garner, Bibber and King (loc. cit) pointed out that the higher hydrocarbons all exist in two enantiotropic forms cx and 6 • The & form is stable at the melting point end changes into the 6 form at temperatures a few degrees below the melting point. The transition temperature of pure dicetyl was found to be 63.5°C. It will be noted that from figure (2) the curve changes its curvature at about 61°C. This may be taken as the transition point of the o< into (3 form. As can be seen from the curve, near the freezing point of the decalin, the solubility of the dicetyl is extremely small. No eutectic was detected even with a .03 molec . percent dicetyl, indicating possibly a mixed - crystal type of curve. 19

71 Conclusion

1. The cis decalin used had a freezing point of -41.22°c. 2. The dicetyl after fifteen reerystallizations from glacial acetic acid had a melting point of 69.55°C, agreeing with that of Piper. 3. The solubility of dicetyl in cis decalin was determined. 4. The affect of a saturated dieylie ring compound on the dicetyl is almost the same as that of a mono-cylic ring compound. 20

Bibliography

1. S. Y. Pilat and M. Godlewicz, Oel und Kohle, 11, 655 (1935) 2. Kling, German Patent 362, 458 3. W. F. Seyer and R. Fordyce, J. A. C. S. 58, 2029 (1936) 4. W. F. Seyer, J. A. C. S. 60, 827 (1938) 5. Hildebrand,

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