Loyola University Chicago Loyola eCommons
Dissertations Theses and Dissertations
1990
¹⁷O and ³³s Nuclear Magnetic Resonance Studies of Some Selected Sulfonates: Concentration and Solvent Dependence
Telitha M. Murray Loyola University Chicago
Follow this and additional works at: https://ecommons.luc.edu/luc_diss
Part of the Chemistry Commons
Recommended Citation Murray, Telitha M., "¹⁷O and ³³s Nuclear Magnetic Resonance Studies of Some Selected Sulfonates: Concentration and Solvent Dependence" (1990). Dissertations. 2893. https://ecommons.luc.edu/luc_diss/2893
This Dissertation is brought to you for free and open access by the Theses and Dissertations at Loyola eCommons. It has been accepted for inclusion in Dissertations by an authorized administrator of Loyola eCommons. For more information, please contact [email protected].
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License. Copyright © 1990 Telitha M. Murray 170 AND 33S NUCLEAR MAGNETIC RESONANCE STUDIES OF· SOME SELECTED
SULFONATES. CONCENTRATION AND SOLVENT DEPENDENCE.
by
TELITHA M. MURRAY
A Dissertation Submitted to the Faculty of the Graduate School
of Loyola University of Chicago in Partial Fulfillment
of the Requirements of the Degree of
Doctor of Philosophy
July
1990 Talitha M. Murray
Loyola University of Chicago
170 AND 33S NUCLEAR MAGNETIC RESONANCE STUDIES
OF SOME SELECTED SULFONATES:
CONCENTRATION AND SOLVENT DEPENDENCE.
The solvation of the sulfonate anion has been
investigated using 170 and 338 NMR over a range of anion
concentrations for a number of solvents. Both 170 (I=5/2) and 338 (!=3/2) are rapidly relaxing, quadrupolar nuclei of low natural abundance. The methanesulfonate anion (M8A) , the simplest of the organic sulfonates, is approximately
tetrahedral at sulfur and displays relatively narrow sulfur resonances. Plots of inverse linewidth versus concentration are, for both nuclei, linear between 8 M and 0.2 M. In order to confirm the linewidth at infinite dilution, low concentrations of aqueous methanesulfonic acid sodium salt (M8A88) with stoichiometric amounts of 18-Crown-6 (to sequester the cation) were evaluated and extrapolated to 71 Hz (1 7 O) and 31 Hz ( 338) . While the 17 o resonance was broader, the 338 linewidth agreed to within 10% of the protonated species at infinite dilution. The aqueous solvation of trifluoromethanesulfonic acid
(TFMSA) was investigated. The 33S NMR of TFMSA exhibited resonances far broader than those for either MSA or MSASS due to a loss of symmetry as a result of the much larger fluorine atoms. However, 170 displayed narrower linewidths over the entire concentration range as a result of acid autoionization.
Inverse linewidth versus concentration plots for 33S revealed an analogous break above 5 M. 33S and 170 chemical shifts were observed 20 ppm upfield from the non-fluorinated analogs. 170 AND 33S NUCLEAR MAGNETIC RESONANCE STUDIES OF SOME SELECTED
SULFONATES. CONCENTRATION AND SOLVENT DEPENDENCE.
by
TELITHA M. MURRAY
A Dissertation Submitted to the Faculty of the Graduate School
of Loyola University of Chicago in Partial Fulfillment
of the Requirements of the Degree of
Doctor of Philosophy
July
1990 ACKNOWLEDGEMENTS
I am grateful to Dr. David S. Crumrine for his guidance and patience during the course of these investigations. without his encouragement, this work would not have come to fruition. Special thanks are due to Dr. A. Keith Jameson, Dr. David Lankin, Dr. Daniel Graham and Dr. Elliott Burrell for their helpful suggestions. Thanks are due to Dr. Duarte Mota de Freitas, Dr.
Charles M. Thompson, the faculty, staff and graduate students of the Department of Chemistry for their support and friendship.
To my parents, Alma and Michael Robinson, brother,
Geoffrey and friends, thank you for your love and support over the years.
I would like to acknowledge the Loyola University of
Chicago Department of Chemistry for its support and the State of Illinois for the Illinois Minority Graduate Incentive
Program Fellowship.
ii VITA
Telitha Marie Murray is the daughter of Alma and Michael Robinson. She was born March 9, 1957 in Los Angeles, California. She has one brother, Geoffrey. Her elementary education was obtained at st. Brigid's and St. Michael 's parochial school in Los Angeles. Her secondary education was completed in 1974 at Immaculate Heart High School in Hollywood, California. In September, 1974, she entered Loyola Marymount University in Marina Del Rey, California as a mathematics major. The following spring, she began a five year hiatus from her studies. In the spring of 1980, she returned to Loyola to pursue a B. S. in chemistry. During that time, she was involved with the department's chemistry society as well as a student member of the American Chemical Society (ACS). Prior to completion of her undergraduate training, Ms. Murray served as a researcher in immunology at Charles Drew Medical School in Los Angeles. In August, 1983, she entered the University of Arizona in Tucson. Under the direction of Dr. Stephen Kukolich, she studied gas phase van der Waal's complexes using microwave spectroscopy. She served as a teaching assistant in both general and physical chemistry. In August 1986, she
iii transferred to Loyola University of Chicago. Directed by Dr. oavid s. Crumrine, she studied solvation phenomenon using 170 and 33s Nuclear Magnetic Resonance spectroscopy. In April, !989, Ms. Murray participated in the 19th annual Loyola Sigma xi Graduate Student Forum and was awarded "Honorable Mention. " In May, 1989, she gave a talk entitled "Nuclear Magnetic
Relaxation Studies of 170 and 33S in Methanesulfonic Acid: concentration and Solvent Dependence. A Brief Comparison to Benzenesulfonic Acid." at the 22nd ACS Great Lakes Regional
Meeting in Duluth, Minnesota. In September, 1989, she delivered a talk entitled " 170 and 33S NMR Studies of the Methanesulfonate Anion" at the 198th National ACS conference in Miami Beach, Florida. In August, 1989, Ms. Murray was granted an assistantship in chemistry at Loyola. She will complete her studies in July, 1990.
iv TABLE OF CONTENTS
ACKNOWLEDGEMENTS . . . • ...... ii ... VITA . · · · · · . • . • • • . . • • • . • • . • • • • . 111 DEFINITION OF TERMS ...... vi
LIST OF TABLES ...... vii LIST OF FIGURES ...... ix
CONTENTS OF APPENDICES . xi
CHAPTER I. INTRODUCTION ...... 1
1. 170 NMR . . . . . 4
la. 170 Chemical Shifts 5 lb. 170 Linewidths . . 9
2 • 33S NMR • • . . . . 9
2a. 33S Chemical Shifts . • • • . 10 2b. 33S Linewidths . . . . • .12
3. Solvents . . . 12
4. Statement of Problem . . . 22
II. EXPERIMENTAL • • • 2 3
III. RESULTS .. 27
1. Water ...... 27 2. Alcohols ...... 49 3. Amides ...... 55 4. Ethers ...... 59 5. Acetonitrile ...... 63 6. Acetone and DMSO ...... 67 IV. DISCUSSION . 72
CONCLUSION . • • 89 v REFERENCES 92
APPENDIX A 98
APPENDIX B 112
vi DEFINITION OF TERMS
gyromagnetic ratio in rad T- 1s-1 t3 c carbon-13 0 chemical shift in ppm efg electric field gradient € dielectric constant p viscosity H proton; essentially 100% natural abundant I nuclear spin quantum number µ. dipole moment in D (Debye) NMR nuclear magnetic resonance 'ff pi Q nuclear quadrupole moment RF ~adio frequency portion of the electromagnetic spectrum density in g ml -l diamagnetic shielding paramagnetic shielding total shielding spin-lattice relaxation; longitudinal relaxation in s-1 1 Tz spin-spin relaxation; transverse relaxation in s- re reorientational correlation time in s x electronegativity full linewidth at half height (FWHH) in Hz
RR'CO carbonyl; R = H: aldehyde
Acetone (CH 3 ) 2CO CAR methylcarbi tol i CH30CH2CH20CH2CH20H DME dimethoxyethane; CH30CH2CH20CH 3 DMF N,N-dimethylformamide; HCON(CH 3 ) 2 DMSO dimethylsulfoxide; (CH 3 ) 2SO EtOH ethanol ; CH 3CH20H FAD formamide; HCONH2 Me OH methanol ; CH30H MSA methanesulfonic acid; CH3S03H MSASS methanesulfonic acid sodium salt NMF N-methylformamide; HCOHN(CH 3 ) TFMSA trifluoromethanesulfonic acid; CF 3S03H THF tetrahydrofuran; ( CH2 ) 40
vii LIST OF TABLES
Solvent Y-values . . 21 Solvent Z-values . 21
3. Solvent ET-values 21
4. NMR Experimental Parameters . 25
5. Physical Constants for a Variety of Solvents . . 26 6. Linewidth Dependence on Concentration in Aqueous Methanesulfonic Acid ...... 31
1. 170 Chemical Shift Dependence on Concentration in Aqueous Methanesulfonic Acid ...... 34
8. 33S Chemical Shift Dependence on Concentration in Aqueous Methanesulfonic Acid ...... 34
9. Concentration Dependence on Interpolated Degree of Ionization in Aqueous Methanesulfonic Acid . . . 36
10. Concentration Dependence of 170 and 33s Chemical shifts and Linewidths of Methanesulfonic Acid Sodium Salt with 18-Crown-6 ...... 41
11. Concentration Dependence of 170 and 33S Chemical Shifts and Linewidths of Trifluoromethanesulfonic Acid in Water ...... 45
12. Concentration Dependence of 170 and 33S Chemical Shifts and Linewidths of Trifluoromethanesulfonic Acid in Water at 50±1°C ...... 45
13. Concentration Dependence of 170 Chemical Shifts and Linewidths of Methanesulfonic Acid in Methanol and Ethanol . . . . • ...... 50
14. Concentration Dependence of 33S Linewidths of Methanesulfonic Acid in Methanol and Ethanol . . . . 50
15. 170 and 33S - Comparison of the Viscosity Non-corrected and Viscosity Corrected Linewidths at Infinite Dilution for Methanesulfonic Acid in Methanol and Ethanol ...... 54
viii concentration Dependence of 170 Chemical Shifts 16· and Linewidths of Methanesulfonic Acid in Formamide, N-Methylformamide and N,N-Dimethylformamide . . . . • ...... 56
33 17. concentration Dependence of S Chemical Shifts and Linewidths of Methanesulfonic Acid in Formamide, N-Methylformamide and N,N-Dimethylformamide ...••...... •.. 56
33 18. 170 and S - Comparison of the Viscosity Non-corrected and Viscosity Corrected Linewidths at Infinite Dilution for Methanesulfonic Acid in Formamide, N-Methylformamide and N,N-Dimethylformamide •...... 56
19. concentration Dependence of 170 Chemical Shifts and Linewidths of Methanesulfonic Acid in Tetrahydrofuran, Dimethoxyethane and Methyl Carbitol ...... 60
20. Concentration Dependence of 33S Chemical Shifts and Linewidths of Methanesulfonic Acid in Tetrahydrofuran, Dimethoxyethane and Methyl carbi tol ...... 60
21. 170 and 33S - Comparison of the Viscosity Non-corrected and Viscosity Corrected Linewidths at Infinite Dilution for Methanesulfonic Acid in Tetrahydrofuran, Dimethoxyethane and Methyl Carbitol ...... • ...... 60
22. Concentration Dependence of 170 and 33S Chemical Shifts and Linewidths of Methanesulfonic Acid in Acetonitrile ...... • ...... 64
23. Concentration Dependence of 170 and 33S Chemical Shifts and Linewidths of Methanesulfonic Acid in Acetone and Dimethylsulfoxide ...... 68
24. Summary of Linewidths at Infinite Dilution and Calculated Spin-Lattice Relaxation Times for Methanesulfonic Acid in a Variety of Solvents . . . 71
ix LIST OF FIGURES
17 1. Methanesulfonic Acid in Water; 0 Inverse Linewidth versus Concentration ...... 28
33 2. Methanesulfonic Acid in Water; S Inverse Linewidth versus Concentration . • ...... 29
3. Methanesulfonic Acid in Water; 170 Inverse Linewidth Comparison Between Methanesulfonic Acid and Water Linewidths ...... 32
4. Methanesulfonic Acid in Water; 170 Chemical Shifts versus Concentration . • ...... 33
5. Methanesulfonic Acid in Water; 170 Degree of Ionization versus Inverse Linewidth . . . . 37
6. Methanesulfonic Acid in Water; 33S Degree of Ionization versus Inverse Linewidth • . . . . . 38
7. Methanesulfonic Acid Sodium Salt/18-Crown-6 in water; 170 Inverse Linewidths versus Concentration ...... 42
8. Methanesulfonic Acid Sodium Salt/18-Crown-6 in water; 33S Inverse Linewidths versus Concentration . • • ...... 43
9. Trifluoromethanesulfonic Acid in Water; 170 Inverse Linewidth versus Concentration at 20±1"C and 50±1"C ...... 46
10. Trifluoromethanesulfonic Acid in Water; 33S Inverse Linewidth versus Concentration at 20±1"C and 50±1"C ...... •...... 47
11. Trifluoromethanesulfonic Acid in Water; 170 Chemical Shift versus Concentration ...... 48
12. Methanesulfonic Acid in Methanol and Ethanol; 170 Inverse Linewidths versus Concentration . . . . 51
13. Methanesulfonic Acid in Methanol and Ethanol; 33S Inverse Linewidths versus Concentration . . . . 52 x Methanesulfonic acid in Formamide, 14- N-Methylformamide and N,N-Dimethylformamide; 110 Inverse Linewidths versus Concentration 57
15. Methanesulfonic acid in Formamide, N-Methylformamide and N,N-Dimethylformamide; 335 Inverse Linewidths versus Concentration 58
16. Methanesulfonic Acid in Tetrahydrofuran, oimethoxyethane and Methyl Carbitol; 170 Inverse Linewidths versus Concentration 61
11. Methanesulfonic Acid in Tetrahydrofuran, and Dimethoxyethane; 335 Inverse Linewidths versus Concentration . . . . 62
18. Methanesulfonic Acid in Acetonitrile; 170 Inverse Linewidths versus Concentration 65
19. Methanesulfonic Acid in Acetonitrile; 338 Inverse Linewidths versus Concentration 66
20. Methanesulfonic Acid in Acetone and Dimethylsulfoxide; 170 Inverse Linewidths versus Concentration . . . . 69
21. Methanesulfonic Acid in Acetone and Dimethylsulfoxide; 338 Inverse Linewidths versus Concentration . . . . 70
xi CONTENTS OF APPENDICES
A. Regression Analyses ...... 98
B. Representative Spectra ...... 112
xii CHAPTER I
INTRODUCTION
In the Nuclear Magnetic Resonance experiment, oxygen-17
5 33 3 (110; I= / 2 ) and sulfur-33 ( S; I= / 2 ) have the same order of magnitude receptivity relative to the proton (approximately
17 33 10-5 ) • 0 and S are rapidly relaxing, quadrupolar nuclei of
17 33 low natural abundance ( 0 - 0.037%; S - 0.76%). Rapid quadrupolar relaxation leads to broad resonances, poor resolution and low signal-to-noise, 1 but permits faster RF pulsing that somewhat offsets the long data collection times necessary for signal enhancement. The linewidths for both nuclei are expected to be far greater than those usually observed for either 1H or 13C. Sulfur resonances are difficult to observe when the nucleus is in an unsymmetrical environment. Tetrahedral surroundings diminish its quadrupolar nature and contribute to a narrowing of the spectral line. The nearly spherical environment of sulfur in some simple compounds provides a basis for future studies of less symmetric nuclei in higher magnetic fields.
The American Petroleum Institute has reported2 that sulfur is essentially present in oils as sulfides (-Sn-) . Differentiation between aliphatic, aromatic, cyclic and 2
thiophenic sulfides has proven difficult. 3 Sulfur-33 chemical
shifts are said to be less sensitive to structural changes
than those of oxygen-17. 4 This phenomenon is evidenced in the
present work. 170 NMR has been used as a diagnostic tool in
the study of complex biological systems. 5 In 19 7 9, Kosugi and Takeuchi 6 reported the results of 13C
titration shifts (changes in the chemical shift as a result
of protonation or deprotonation) of some selected sulfonic
acids - important in the determination of pKa and pKb values
and structure elucidation. KA and KB refer to acid and base dissociation constants (pK = -log K) . Oxygen-17 has also been used in the analysis of aqueous alkaline silicate solutions. 7
A fundamental understanding of the structure of these
compounds can provide a basis for the analysis of the rocks,
minerals and soils found on the surface of the earth.
For highly acidic solutions, pH measurements are not
possible. In order to ascertain the hydrogen-ion activity,
aH+, a scale describing the behavior of a base which is not
completely dissociated in the acid must be designed. Hammett8
proposed an acidity function based on the activities of the
species present in solution:
Ho = pKA - 1 og I [1] where I is defined by
1 I = [2]
Superacids are capable of protonating extremely weak bases 3
(e.g., benzene). Acidity functions as high as -20 on the Hammett scale have been achieved. Organic sulfonic acids and their halogenated counterparts possess both hydrophobic (hydrocarbon) and
hydrophilic groups. These compounds are termed amphipathic and
exhibit limited solubility in aqueous media. High concentrations of these compounds tend to self-associate in
9 10 11 such a way that their hydrophobic tails form a liquid-like • • core leaving their hydrophilic polar heads exposed to the surrounding medium. The result of this aggregation is a micelle. Compounds of this type exhibit a critical micelle concentration (CMC) above which they exist in aqueous media almost entirely in micellar form. In theoretical models of these solutions, water is considered a continuous dielectric medium. Inhomogeneities in the distribution of water molecules about the surface of these aggregates is defined by
12 13 14 the hydration number ' ' - the number of water molecules that move with the surfactant as a kinetic entity. 15 Typically, this number is 4 to 10. However, methanesulfonic acid is the
smallest of the organic sulfonic acids and is highly soluble in aqueous media. Uedaira and Uedaira16 have determined the hydration number of methanesulfonic acid as 13 - one acid molecule surrounded by thirteen water molecules. The hydrophilic-lipophilic balance (HLB) is defined as the molecular weight of the hydrophilic portion of the 4 molecule divided by the molecular weight of the hydrophobic portion. An analogous but opposite trend arises when these compounds are in organic media. The extent of aggregation is dependent on the length of the hydrophobic chain an increased number of -CH2- groups encourages micelle formation. Although the sulfonic acids investigated here do not possess long alkyl chains, the potential for micelle formation required investigation. Pottel, Kaatze and Muller17 examined the dielectric relaxation of zwitterionic (a single species possessing both positively and negatively charged groups) surfactant micelles in aqueous media. The surfactants used contained at least eleven -CH2- groups. The positively charged (cationic) groups consisted of -H3CN+CH3- or -N+H 2-.
The negatively charged (anionic) species were -C02-, -S03 - or
-P04--. They developed a model for the relative geometry of micelles depending on chain length and polar head group.
1. 170 NMR
Oxygen-17 exhibits a large chemical shift range
(approximately 1600 ppm) - the chemical shift differences being a result of structurally nonequivalent nuclei . 18 The chemical shift is characteristic of a specific chemical environment, but it is troublesome to account for the large chemical shifts found for compounds containing oxygen-oxygen bonds. The resonance linewidths are proportional to the correlation time for molecular reorientation. 19 170 ·NMR can 5 be used to unequivocally distinguish between nonequivalent oxygen atoms.
While 170 NMR has been used extensively in the identification and classification (chemical shift and linewidth data) of various compounds, little has been done in applying this knowledge to other physical phenomenon (i.e., solvat ion) .
1 a. 170 Chemical Shifts Oxygen is one of the most important atoms in hydrogen bonded systems because it acts as both a proton acceptor and proton donor. 20 The effects of oxygen bonding on chemical shift have been explored using the magnetic resonance technique. The variation in 170 chemical shifts is determined mainly by the paramagnetic term of the nuclear shielding
21 22 constant (or) • '
Or = On+ Op [3] H. A. Christ23 was one of the first researchers to investigate oxygen-17 NMR chemical shifts of a variety of compounds. studying a group of common solvents, the measured 6-values for MeOH, EtOH, THF and DMSO, relative to water, were
37, 5, 19 and 13 ppm respectively. However, the chemical shifts for the doubly bonded oxygens in acetone and formamide occurred at 568 and 306 ppm respectively. In general, it was found that aldehyde chemical shifts occurred between 580 and
600 ppm. The relatively small deviation from the reference 6 for DMSO is a result of oxygen shielding by the sulfur nucleus. In a later work, Christ et al. 24 examined the effects of various substituents on the chemical shifts of oxygen-17. They found that the resonance of singly bonded oxygen is shifted to low field by all of the substituents studied except
-CH3 • The effects of atoms directly bonded to oxygen increase according to H, c, s, Cl < N < O. In carbonyl compounds, the resonance of doubly bonded oxygen is shifted to high field by all substituents. In 1986, Barbarella, et al. 4 examined the effects of substitution on the S02 moiety (X-S02 -Y) . They found that o (170) decreased as the electronegativity of both ligands increased and that there was no linear relationship between the chemical shifts and the electronegativities of X and Y. The chemical shift of oxygen is extremely sensitive to the effects of structural changes due to the presence of nonbonding electrons on the oxygen atom. Chimichi, Nesi and De Sio25 studied the effects of substitution at the a-carbon in five-membered heterocyclic derivatives. In accordance with the trend observed for dialkyl and alkyl vinyl ethers, alkyl substitution at this site gives rise to an additive downfield shift (tio = 7.5 - 8 ppm). They ascribed these changes to the sum of the electronegativities of the atoms linked directly to the central oxygen. 170 chemical shifts have been used in the study of 7
organosulfur compounds (cyclic sulfones) . 26 It was found that there was a marked variation in the shifts with ring size.
The 170 of the four-membered ring was considerably deshielded with respect to the three-, five- and six-membered rings. The sulfoxides also followed this trend. Dyer, Harris and Evans27 studied the chemical shifts of a number of cyclic and acyclic, aliphatic, olefinic and aryl sulfoxides and sulfones. While the 170 chemical shifts of aliphatic, acyclic sulfoxides occur between +20 ppm and -20 ppm, the corresponding sulfones were between 120 and 183 ppm relative to external water. The increase in the double bond character of the sulfones stems from the effect of the "contracted" 3d orbitals of the sulfonyl sulfur. This allows a more efficient overlap with the smaller oxygen 2p orbitals.
It was found that the breaking of hydrogen bonds
involving the oxygen atoms of water, acetic acid and methanol leads to an upfield shift of the 170 resonance: -12 ppm for proton donation and -6 ppm for proton acceptance. Oxygen-17
NMR has been used in structure and conformation elucidation.
Prior to 1985, little was known about steric effects on 170 chemical shifts. In 1984, Balakrishnan et al. 28 studied the substituent effects on 170 chemical shifts for para-substituted benzoic acids, methyl benzoates, cinnamic acids and cinnamates. They confirmed that ~-electron density was the major factor determining 170 substituent chemical shift (SCS). Boykin and 8
saumstark29 have used 170 as a probe for evaluating electronic distribution. These studies involved the effects of torsion angle and charge density on chemical shift values. The same
30 year, Baumstark et al. probed the electronic and conformational effects of steric interactions in hindered N- substituted imides. They concluded that the nontorsional 170 chemical shifts observed for the anhydrides were indicative of repulsive van der Waals interactions. Chang and le Noble31 used 170 NMR in their study of ion-pairing and the rotational motion of oxyanions using shift reagents. Oxygen-17 relaxation has also been used to study the
solvation of oxygen/sulfur systems in aqueous solutions of
the sulfate ion (SO/-). 32 Based on ab initio calculations, the
electric field gradient at oxygen has been calculated. Because sulfur is in a spherical environment, its efg is zero
and the only gradient is that of oxygen. These studies facilitated the examination of the hydration of the nucleus.
Copenhafer and Rieger33 studied oxygen-17 exchange between the arsenite ion and solvent water. They determined that the chemical shifts are generally downf ield from water by 200 ppm. The first-order oxygen exchange processes corresponded to a nucleophilic displacement by water on arsenite. 9
17 1 b . 0 Linewidths While 170 is a quadrupolar nucleus, a number of experimental conditions may be employed to decrease the resonance linewidth. Linebroadening due to solute/solvent 170 exchange is minimal. Linewidths may be minimized by conducting experiments at elevated temperatures and low sample concentration in a solvent having low viscosity. 1 Large molecules must be observed in very dilute solutions.
Jackson and Taube34 investigated the NMR absorption for
170 in oxy ions. They observed linebroadening due to electron exchange between Mn0 4 - and Mn0 4 z-. While the linewidths were insensitive to low concentrations of dichromate (Na2 Cr20 7 ), they were responsive to the introduction of perchloric acid
(HClOd. It was concluded that the linebroadening was a result of a linear variation in H+.
2. 33S NMR
Although 33S is found in greater natural abundance than
170, observation of this isotope is exacting. It is the combination of low natural abundance, small gyromagnetic ratio
7 1 1 26 2 ( -y = 2. 055x10 rad T- s- ) and moderate (Q = -5. 5xl0- m ) quadrupole moment of the 33S nucleus that makes the NMR experiment difficult. 35 The gyromagnetic ratio is indicative of the orientation of the nuclear spin relative to the magnetic moment with a negative value implying an antiparallel orientation. Because its detection is, in large part,· reliant 10
on its geometric surroundings, 33S is most easily observed when
in a spherical environment. 36 Small sulfur-containing
molecules with symmetric electronic distributions about sulfur
have provided useful information about the nucleus. 37
Linebroadening due to an enhanced efg can obliterate the
resonance and sequester it to the baseline. 38 Al though
sulfur/hydrogen coupling for a 2 M solution of butadiene
sulfone has been observed, 39 the only measured sulfur coupling
33 19 19 constant appears to be J( S, F) = 251 Hz in SF6 •
2 a. 33S Chemical Shifts
The regions in which the chemical shifts of 33S are
observed are governed by four distinct circumstances: 38
a. singly bonded sulfur
b. multiply bonded sulfur
c. sulfur participating in a delocalized system
d. sulfur bonded to one or more oxygens.
The sensitivity of the 33S chemical shift to electronic and solvent changes is less than that of 170. 19 The 33S chemical shifts for sulfones and sulfonic acids (and their derivatives) occur, on the average, between 310 and 390 ppm downfield relative to external carbon disulfide, CS 2 (CS 2 is 328 ppm downfield from the sulfate reference). 32 Faure, et al. 40 have reported the chemical shift of MSA, relative to external (NH 4 ) 2S04 , as -5±2 ppm. As an alkyl chain increases 11
in length, the sulfur-33 chemical shifts are essentially invariant. As with oxygen-17, the chemical shift of sulfur
33 moves to lower frequency (6 = upfield) as the
electronegativity of the ligands on X-802-Y decrease. Harris and Evans41 have attempted to cultivate an analytical technique for the analysis of coal and petroleum
extracts using the effects of substitution on the -802- moiety. They observed a number of interesting trends. Upon symmetric substitution, an increase in the alkyl chain length, the sulfur resonance was shifted slightly downfield; bulky groups such as isopropyl and isobutyl had an enhanced and similar effect. When bonded to an aromatic system, increased shielding induced an upfield shift. Annunziata and Barbarella42 have reported similar findings. In general, the chemical shift of 33 8 increases as the electronic charge on sulfur decreases. Aromatic sulfonic acids are more shielded than their
aliphatic counterparts; as a result, the resonances occur upfield. In agreement with Faure, 4° Crumrine and Gillece Castro43 found the chemical shift for methanesulfonic acid to be approximately -5 ppm upfield from aqueous ammonium sulfate. In 1989, French and Crumrine44 reported the concentration and solvent dependence of 33 8 in benzenesulfonic acid. The approximate chemical shifts (relative to external, aqueous 4
M (NH4) 2804) in water, FAD and NMF were found to be -11, -12 and -13 ppm respectively. This represents an average shift 12 of approximately 7 ppm upfield from the methanesulfonic acid resonance for the aforementioned solvents. They further found that there is no linear correlation between the sulfur linewidth of the benzenesulfonate anion and solution viscosity - the viscosity of the solution increases more rapidly with increasing concentration than does the linewidth.
2 b. 33S Linewidths Sulfur linewidths vary greatly depending on chemical environment and solvent. The narrowest resonances are achieved when the nucleus is present in a symmetric environment. A decrease in symmetry severely affects the linewidth. For example, the loss of one oxygen atom on going from CH3S02 CH 3 to CH3SOCH3 , causes the linewidth to change from
50 to 5400 Hz. 42 Often, a lack of symmetry about the sulfur nucleus can confine the signal to the baseline rendering it undetectable.
3. Solvents
The selection of solvent is not arbitrary. 1 One must be certain that it is not reactive toward the compound to be studied - sample decomposition must be avoided. Because linebroadening is enhanced in solvents of high viscosity, care must be taken in choosing media which encourage long nuclear relaxation times. The solvent should possess an high boiling point in order to be useful in experiments requiring elevated 13
17 33 18 19 temperatures. 0 and S NMR studies ' of neat solvents revealed linewidths far greater than those encountered for either 1H or 13C. The degree of order in the liquid phase changes rapidly. TWO forces which stabilize liquids are Coulombic interactions
(electrostatic) and hydrogen bonding/charge transfer (donor acceptor). H-bonding usually involves an electron donor group
(-OH, -OR, -F, carbonyl and -NR2 ) and an hydroxyl group (-OH: acceptor) . The interactions are described by HOMO-LUMO stabilizations. Solvents are described by a number of physical characteristics. Di polar aprotic solvents possess large dipole moments, but, have no hydrogen bonding capabilities. 45 Protic liquids are more ordered in bulk media due to additional organization by H-bonding. The polarity of a solvent describes its capacity to solvate and stabilize charges. Isaacs45 stated that,
Any phenomena, chemical or physical, which are sensitive to the nature of the solvent may be made the basis of a solvation index ..... (the solvation index) depends upon the nature of the solvation forces to which the experiment responds.
It was the objective of this work to attempt to develop a
"solvation index" based on a solvent's effect on the linewidths and chemical shifts of 170 and 33S in some selected organic sulfonic acids. 14
46 47 48 49 Gutmann • • • developed a set of solvent parameters - donor numbers (DN) and acceptor numbers (AN). Donor numbers are an enthalpic measure of the capacity of a solvent (S:) to donate an electron-pair to antimony(!!!) chloride (SbC13 ) in dilute dichloroethane solutions. Acceptor numbers are built on the proficiency of an electron acceptor solvent (S) to affect a chemical shift to the 31P NMR of triethylphosphine oxide (Et3 PO). They are proportional to the magnitude of the interaction. Experiments are conducted in dichloroethane solution with a test solvent and SbC13 •
51 Deverell 5°· proposed a model relating the attractive and repulsive forces of solute and solvent molecules. Repulsive forces were found responsible for distortions from spherical symmetry of the ionic electron clouds of the solute. The product of this distortion is an electric field gradient.
From this, Deverell determined the magnitude of the relaxation rate of the ionic nucleus. The advantage of this approach is that some parameters which are integral to the electrostatic
52 53 model are not needed. However, Hertz ' has shown that omission of electrostatic terms cannot be justified. It was demonstrated that, in aqueous solutions, water-water and ion ion correlations assist in the explanation of relaxation rates in electrolyte solutions. The choice of aqueous medium was an attempt at a simpler presentation. This treatment is general and may be applied to non-aqueous solutions.
Weingartner and Hertz54 studied the magnetic relaxation 15 interactions of quadrupolar nuclei in non-aqueous electrolyte solutions. Using methanol, ethanol, formic acid, formamide,
NMF, DMF, acetone, acetonitrile and DMSO, they developed three models for solvation. The "Fully Random Distribution" model
(FRD) [4] assumes a uniform distribution of solute centers and a random orientation of solvent dipoles. In this instance, a solvation sphere is absent. The "Non-Oriented Solvation" model (NOS) [5] assumes a well defined first solvation sphere with randomly oriented solvent dipoles. The "Fully Oriented
Solvat ion" model (FOS) [ 6] proposes a well defined first solvation sphere and radial orientation of solvent dipoles in the sphere.
2 41T m CsolvTc [4] 9
2 5 m n5 Tc d = d 2 = + d*(b) = [5] 9
A + d* (b) • [6] d describes the structure of the solvent dipoles around a uniform distribution of ionic centers. m is the electric dipole moment of the solvent molecule, csolv the dipole
3 concentration in particles cm- , r 0 the closest distance of approach between the center of the ion and the point dipole and re the correlation time describing the fluctuation of the 16 efg. These models only address primary solvation. The orientation of the bulk solvent dipoles are described by d" (b): the FRD of solvent dipoles. In the FOS model, A = (1-e-~) where A represents the magnitude of the quenching of the efg. comparing solute linewidths in various solvents is essentially a study of the changes of the electric field gradients imposed on the resonant nuclei. Changes in the correlation times affect linewidths and obscure the effects of a varying electric field gradient. Berman and Stengle55 used 35Cl NMR to defined three distinct classes of solvents. The first group exhibits narrow linewidths essentially constant over a range of chlorine-35 concentrations. In water, DMSO and DMF, the linewidths were characteristic of media possessing high dielectric constants and high basic strengths (Gutmann donor numbers) . These factors combined to prevent ion association. The second group (propanol, butanol and ethylacetate) promotes extensive contact ion association and large concentration-dependent linewidths. These solvents are characterized by low dielectric constants and moderate Gutmann donor numbers. The third group (acetone, methanol, ethanol, acetonitrile and propionitrile) encourage intermediate linewidths. These solvents favor an intermediate degree of ion association. They possess middle range dielectric constants and Gutmann donor numbers. For this work, water was the primary solvent because its 17
'cal and dynamic properties have been extensively studied chem1 and are readily. avai'l a bl e in. the l 1't era t ure. 53,56,57 Because the solutes used were relatively small organic sulfonic acids, problems with immiscibility were not encountered. An additional benefit of aqueous medium is that it provides an internal reference for 170 spectra thereby eliminating the occasional necessity for magnetic susceptibility corrections. The similar hydrogen bonding capabilities and structure promoting behavior of the alcohols furnished a natural deviation from aqueous solutions. The 170 resonances of primary alcohols such as methanol (MeOH) and ethanol (EtOH) occur near the water reference. 19 The point dipoles in methanol and ethanol are located in the oxygen atom and assume approximately the same Pauling ionic radius of solvation as
54 water: rsolv = 1. 4 A. The 170 resonances of the carbonyl groups of formamide,
NMF and DMF occur far downfield from the water resonance. 19
The ionic radius of solvation for the amides is estimated to be approximately 1.8 A. 54 Formamide is an highly organized, hydrogen-bonding solvent possessing no hydrophobic groups. 58
The hydrogen-bonding capability of the molecule produces a large effective molecular radius. 59 The f ormamide molecule may be assumed to be essentially planar with rotation of the NH2 group around the c-N bond being slow compared to the reorientation of the molecular framework. The relaxation 18 rates of ions in aqueous solutions are lower than the corresponding ion in f ormamide. This is an effect of the high dipole moment and the long reorientational correlation time
of the formamide molecule. Liquid NMF is highly associative due to its dielectric relaxation, extremely high dielectric constant and self-diffusion coefficients. 58 DMF is an aprotic solvent with two hydrophobic groups. The mass of DMF and its electric dipole moment contribute to an extreme retardation of the correlation time and the solvent "sees" only an
59 60 hydrophobic hydration sphere. • The rotational correlation time in pure DMF is nearly the same as that of water. While the 170 chemical shift of acetone occurs at
approximately 572 ppm, 19 DMSO is 17 ppm downfield from water. The reorientation correlation time of the DMSO molecule in the pure solvent is high - there is a tendency toward self association. 59 This is evidenced in the viscosity of pure DMSO
(ry = 1.96 cP) in comparison with that of acetone (ry = 0.3 cP). In experiments conducted using Al(III) complexes, 61 DMSO is a strong donor solvent.
As can be seen, a number of models have been suggested
for the interactions between solutes and sol vents and the determination of solvent parameters. In addition to these, three are based on solvent polarity and the formation or destruction of ion-pairs.
A+B- ----) AB [7]
[8] 19
Solvent Y-values are defined by the reaction rates of
62 63 t-butyl chloride in a variety of solvents. ' Mathematically, they are given by
Y = 1 og k 1 - 1 og k 2 [9] where k 1 is the rate of solvolysis of t-butyl chloride and k 2 is the rate of solvolysis of t-butyl chloride in 80% ethanol.
The n-+1f* and 1f-+7r* transitions of pyridinium ions are only moderately susceptible to changes in substituent, but, 1- alkylpyridinium iodides are extremely sensitive to solvent effects. z-values are solvent parameters based on charge transfer light absorption bands of the pyridinium salt. 64
They represent the transition energy for the longest observed solvent wavelength (A/A) absorption band for a system containing 1-ethyl-4-carbomethoxypyridinium iodide. Two distinct problems arise in the determination of solvent z values. (1) The salt may be insoluble in nonpolar solvents.
Substitution with 1-ethyl-4-carbo-t-butoxypyridinium iodide provides greater solubility. However, one must extrapolate to zero ionic strength as ion-pairing may be augmented in nonpolar solvents and lead to erroneously high z-values. (2)
In solutions containing highly polar solvents, the light absorption band may move to such short wavelength that it is eclipsed by the more intense 1f-+1f* transition of the pyridinium ion. The Y and Z-values for the solvents used in this work are given in the following table.
A solvent polarity parameter, ET, has been proposed by 20
65 66 a number of workers. ' Er-values are based on transition energies for intramolecular charge-transfer bands of the pyridinium phenol betine. Although this ion is much larger than the aforementioned pyridinium iodide, there is a linear correlation between Er-values and z-values. 21
Table 1. Some selected solvents and the corresponding Y values for solutions containing t-butyl chloride. (* = % by volume.)
Solvent Y-value
Water 3.493 Methanol -1. 090 Formamide 0.604 90% Acetone -1. 856*
Table 2 . Some selected solvents and the corresponding z values for solutions containing 1-ethyl-4- carbomethoxypyridinium iodide.
Solvent z-value
Water 94.6 Methanol 83.6 Ethanol 79.6 Acetonitrile 71. 3 Formamide 83.3 N,N-dimethylformamide 68.5 Dimethylsulfoxide 71.1 Acetone 65.7 Dimethoxyethane 62.1
Table 3. Some selected solvents and the corresponding Er val ues/kcal mol-1 for solutions containing pyridinium phenol betaine.
Solvent
Water 63.1 Methanol 55.5 Ethanol 51.9 Acetonitrile 46.0 Formamide 56.6 N-methylformamide 54.1 N,N-dimethylformamide 43.8 Dimethylsulfoxide 45.0 Acetone 42.2 Tetrahydrofuran 37.4 Carbon disulfide 32.6 22
4. Statement of Experimental Problem In the NMR experiment, the relaxation of natural abund ance 170 is enhanced by optimization of experimental conditions. Solvent and concentration variations assist in decreasing electric field gradients and hence, allow the observation of resonances. Because 33S is difficult to detect when the nucleus is in an unsymmetrical environment, three simple (essentially spherical) organic sulfonates were utilized. Extrapolation of 170 and 33S relaxation rates to zero solute concentration allowed the evaluation of ion-ion and ion-solvent effects on quadrupolar relaxation CHAPTER II
EXPERIMENTAL
The NMR spectra of natural abundance 170 and 33S in some simple organic sulfonic acids and a sulfonic acid sodium salt were obtained for a range of acid concentrations and in a variety of solvents. All spectra were acquired on a Varian
VXR-300 FT-NMR spectrometer with a 10 mm broad-band switchable probe at 17 o and 33S spectral frequencies of 4 o. 662 MHz and 23. 008 MHz respectively. Data was accumulated with the sample spinning and the spectrometer unlocked. Quadrature detection was employed. The experimental parameters used for detection of the signals are listed in Table 4.
All reagents were acquired commercially and used without further purification. The solutes studied were liquid methanesulfonic acid, methanesulfonic acid sodium salt with stoichiometric amounts of 18-crown-6 and liquid trifluoromethanesulfonic acid.
The NMR spectra of methanesulfonic acid were acquired in water, formamide, NMF, DMF, acetone, DMSO, THF, DME, CAR,
MeOH, EtOH and acetonitrile (CH 3CN). Some of the physical constants for the aforementioned solvents are listed in Table
5.
23 24 For aqueous methanesulfonic acid, proton coupled spectra at 20±1°c and proton coupled and decoupled spectra at 40±1°C were obtained for a range of acid concentrations. In order to counter the temperature gradients inherent in broadband decoupling experiments, elevated temperatures were employed. The broadband decoupling pulse sequence WALTZ-16 was ut1· 1 ize· d . 67 For the sodium salt, experiments were conducted using stoichiometric amounts of 18-crown-6.
The chemical shifts for 170 and 33S were calculated by the computer and reported relative to internal deionized water and external (sample replacement) 4 M ammonium sulfate respectively. For nonaqueous solvents, the oxygen chemical shifts are reported relative to external deionized water. Magnetic susceptibility corrections might be considered in instances where there was either sample replacement or a concentric tube for the reference material. However, it was found unnecessary because the susceptibility correction is
19 68 small. "
The 170 and 33S linewidths were measured manually with an estimated error of ±10%. Treatment of raw data was accomplished using the LOTUS 1-2-3 regression routine to calculate the best fit lines for the 1000/~v~ versus concentration plots. 25
Table 4. General NMR experimental parameters used in the detection of natural abundance 170 and 33S in some selected organic sulfonic acids.
Spectral Fourier Acquis. Width/Hz PW90/µs Number/K Time/s
50,000 10.0 32 0.048 10,000 50.0 32 0.300 Table 5. Physical constants for a variety of solvents. (* = in aqueous H2S04) Gutmann 2 Solvent p(g/ml) TJ (mNs/m ) µ (D) € DN AN pKa
H20 1. 00 1. 001 1.84 80.1 18 54.8 15.5 Me OH 0.787 0.544 1. 70 32.7 20 41. 3 16
EtOH 0.785 1. 078 1. 69 24.5 19 37.1 18
FAD 1.133 3.764 3.73 111. 0 22 39.8 25
NMF 0.999 1. 65 3.83 182.4 24 32.1 -0.04 *
DMF 0.945 0.802 3.86 36.71 24 16.0 -0.01*
THF 0.889 0.55 1. 63 7.58 20 8.2 -1.97 *
DME 0.862 0.455 1. 71 7.2 7.20 CAR 1.0167 0.348 1. 6 -----
CH3CN 0.777 0.345 3.92 36.2 14 18.9 25
(CH3 ) 2CO 0.785 0.295 2.88 20.7 17 20 * (CH3 ) 2SO 1. 096 1.96 4.06 46.45 19.3 -1.54 CHAPTER III
RESULTS
The following results are divided into solvent classes, i.e. , aqueous, amides, ethers, etc. There will be no subdivisions in terms of solutes.
1. water The salvation of the methanesulfonate anion in aqueous medium was investigated using 170 and 33S NMR for a range of acid concentrations. Methanesulfonic acid is a somewhat viscous liquid and at higher concentrations, is expected to yield broad sulfur and oxygen resonances. Initial experiments were conducted at ambient temperature (20±1°C). In order to confirm the linewidth dependence on temperature, experiments were conducted at 40±1°C in which coupled and decoupled spectra were acquired. Because the temperatures induced by broadband decoupling rarely exceed 40°, 69 we felt this to be a sufficient buffer. Figures 1 and 2 demonstrate a narrowing of the spectral lines and nearly parallel correlations between coupled and decoupled data. As expected, the linewidths decreased with increasing temperature (increased molecular tumbling) as well as proton decoupling.
27 FIGURE I . METHANESULFONIC ACID/WATER 17-0 1000/W VS CONCENTRATION 20 19 18 17 16 15 14 n 13 Ill E 12 u itl. 11 0' 0 10 0 " 9 0 () I 8 I'- " 7 6 x 5 0 4 () x 3 () 2 0 0
0 0 2 6 8 10 12 14 16
CONCENTRATION (M) 0 20C COUPLED () 40C COUPLED x 40C DECOUPLED
l\J 00 FIGURE 2. METHANESULFONIC ACID/WATER
33-S 1000/W VS CONCENTRATION
so
0
40 n [f] E u x :;. 0' D 0 30 ~ D ' If) I 0 [T) [T) 0 x 20 D
10
0 ~ 0 2 6 8 10 12 14 16
CONCENTRATION (M) D 20 COUPLED (> 40 COUPLED x 40 DECOUPLED
l\J \0 30 Above 8 M, a break in the linearity of the concentration
17 33 versus 1000/ ll.v\ data was observed for both 0 and 8. At higher concentrations, the broad lines are representative of protonated acid molecules and acid aggregates (Table 6). An accurate evaluation of the intermolecular interactions in this concentration range is difficult. A plot of M8A concentrations versus both H20 and acid oxygen inverse linewidths (Figure 3) displays the same break in linearity - the solute and bulk solvent are undergoing complementary processes. The linewidth dependence is given by the equilibrium [10]:
Ki Kz RS03H + H20 ~ R803 - • H 30+ ~ [10] The chemical shift dependence on concentration was studied under the three experimental conditions. While the 338 shifts remained constant at approximately -5 ppm (Table 8) , the 170 chemical shifts changed 12-13 ppm (Table 7) over the concentration range (Figure 4). The average correlation for the 170 chemical shift versus concentration plots was 0.99. 31
Table 6. Linewidth dependence on concentration in aqueous solutions of methanesulfonic acid.
170 338 Concentration/M l:.11-\i/Hz t.vli/Hz
14 710 2700 11 430 1000 7.7 200 180 6.9 200 130 5.4 120 74 3.9 96 53 2.7 80 38 1.9 77 33 0.96 65 32 0.48 67 25 0.24 64 28 0.19 66 33 0.15 63 28 FIGURE 3 METHANESULFONIC ACID/WATER
17-0 MSA & WATER 1000/W VS CONC. 19 () 18
17 () 16 D 15 () 14 13 n Ul D E 12 u 3 11 '- 0 () 0 10 0 ' 9 0 I 8 ['- ' 7 6 0 5 B 4 3 () D 2 () D 1 0 2 4 6 8 10 12 14 16
CONCENTRATION (M) D MSA () WATER
w !\.) FIGURE 4 METHANESULFONIC ACID/WATER
17-0 CHEMICAL SHIFT VS CONCENTRATION 178
177
176
175 n 174 E Q Q 173 u f- 172 LL - I (f) 171
_J <( 170 u :L w 169 I u 168 0 f' ' 167
166
165
164
163 0 2 4 6 8
CONCENTRATION (M) D 20C COUPLED o 40C COUPLED X 40C DECOUPLED
w w 34
Table 7. Concentration dependence of aqueous methanesulfonic acid 170 chemical shifts. (C = coupled, D =decoupled)
o/ppm o/ppm o/ppm Concentration/M c 20° c 40° D 40°
7.7 163 165 165 6.9 166 166 166 5.4 168 167 168 3.9 170 171 171 2.7 172 173 174 1. 9 174 174 174 0.96 175 175 176 0.48 176 177 177 0.24 176 177 177 0.19 176 177 177 0.15 176 177 177
Table 8. Concentration dependence of aqueous methanesulfonic acid 338 chemical shifts. (C = coupled, D =decoupled)
o/ppm o/ppm o/ppm Concentration/M c 20° c 40° D 40°
7.7 -4.5 -4.5 -4.5 6.9 -5.0 -4.0 -4.0 5.4 -4.8 -5.2 -5.4 3.9 -5.1 -5.1 -5.4 2.7 -5.1 -4.9 -5.2 1.9 -5.2 -5.1 -5.3 0.96 -5.3 -5.2 -5.2 0.48 -5.4 -5.5 -5.5 0.24 -5.4 -5.5 -5.0 0.19 -5.4 -5.5 -5.6 0.15 -5.4 -5.6 -5.9 35 Covington and Thompson studied aqueous solutions of methanesulfonic acid using proton NMR. They found a nonlinear dependence of the concentration on the degree of acid ionization. The degree of ionization, a., in aqueous solutions of MSA can be calculated using proton chemical shift
. 70 measurement s via
(11] where p is 3x/(2-x) and xis the mole fraction of the solute. oH3o+ and oHA are the chemical shifts for the ionized and unionized acid respectively. a., for methanesulfonic acid in water, has been calculated for a range of concentrations. 70 The results revealed a non-linear dependence of ionization on concentration. For the MSA concentrations in this study, the interpolated values of ionization are given in Table 9. Comparing our concentration and linewidth data to the interpolated degree of ionization values, we found a significant correlation between our 170 and 33 S linewidths and the degrees of ionization. Figures 5 and 6 display the relation between degree of ionization and inverse linewidth.
The correlations, in both cases, were on the order of 0.99. 36
Table 9. Concentration dependence on interpolated degree of ionization values. (* it is understood that a compound cannot be greater than 100% ionized, but 70 these values are within 10% experimental error. )
Interpolated Concentration/M a-values*
0.15 1. 036 0.19 1. 023 0.24 1. 032 0.48 1. 020 0.96 1. 028 1.9 0.9809 2.7 0.9629 3.9 0.9173 5.4 0.8550 6.9 0.7924 7.7 0.7924 FIGURE 5. ME HANESULFONIC ACID/WATER
17-0 DEGREE OF IONIZATION VS 1000/W 1.06
1 . OLJ D D 1 02 D z -0 0.98 D f-- <[ N 0 96 - D z 0 - 0.9'1 lL 0 0.92 w w 0 9 rr l'l w 0 0.88
0 86 <[ I Q_ 0 8'1 _J <[ 0 82 D 0 8
0 78 D
0 76 0 2 4 6 8 10 12 1'1 16 18
17-0 1000/W (ms)
w -..] FIGURE 6 METHANESULFONIC ACID/WATER
33-S DEGREE OF IONIZATION VS 1000/W 1.08
1 06
1 04 D D 1.02 D z 0 1 - f- <[ 0.98 D N- z 0.96 0 - 0.94 LL 0 w 0.92 w D a: l'J 0.9 w 0 0.88
<[ 0 86 I Q_ _J 0 84 <[ 0 82
0 8
0 78 D 0 76 0 10 20 30 LIO
33-S 1000/W (ms)
w OJ 39
1 18-Crown-6 (MW 240 .13 g mol- ) is a macrocyclic polyether
that is capable of binding a sodium cation (Na+) . Crown ethers have particularly large complexation constants for alkali metals. However, this is a reversible process and an
71 72 equilibrium is associated with sodium complexation. • In studies using nitrogen and sulfur substituted macrobicyclic ligands, the efg around the sodium atom was found to increase
as compared to the oxygen analogs. Using 23Na NMR, an excess
of the cation in the presence of the cryptate yields two signals - a result of free and complexed Na+. The presence of two resonances indicated that exchange is slow at 35°C. If stoichiometric amounts of the ether and sodium salt of methanesulfonic acid are used, the aqueous acid is primarily present in its anionic form. This impacts the linewidths for both 170 and 33S. The efg at sulfur is essentially zero and linebroadening is diminished. If no sodium atoms are associated with the acid anion, there are three equivalent oxygen atoms and linebroadening is again diminished. However, as indicated by the 23Na experiments, exchange is slow at ambient temperatures and some residual linebroadening is expected. Aqueous solutions of methanesulfonic acid sodium salt and 18-Crown-6 were studied in order to verify assumptions made about extrapolated linewidths at infinite dilution. The concentrations of methanesulfonic acid sodium salt were between 1.9 M and 0.05 M as it was in this realm that our conjectures could be proved or disproved. At 2 0±1 ° C, 40 the sulfur linewidth at infinite dilution (31 Hz) was within
10% experimental error of the MSA linewidth. However, the oxygen linewidth at infinite dilution is greater than that initially measured. This is a by-product of chemical exchange of sodium ions between the crown ether oxygens and the acid oxygens. The 170 and 33S chemical shifts were approximately constant over the entire concentration range. 41
Table 10. Concentration dependence of 170 and 33S chemical shifts and linewidths of methanesulfonic acid sodium salt + 18-crown-6 in water. (* = no signal observed). ______33 ______170------8 Concentration/M nv 11/Hz o/ppm nv 11/Hz o/ppm 1.9 141 178 47 -6.6 1. 6 123 179 43 -6.6 1. 4 105 178 43 -6.4 1.1 108 177 39 -6.1 0.92 102 177 41 -6.1 0.36 85 177 32 -6.1 0.10 76 177 * * 0.05 63 177 * * FIGURE 7 MSASS + 18-C-6/WATER
17-0 1000/W VS CONCENTRATION 17
16 D 15
14
13 D
12 D n 11 (f) E \_) 10 D D 3: g D '- 0 0 0 8 ' 0 7 I f" ' 6 5
4
3
2
0 0 0 2 0.4 0.6 0.8 1.2 1.4 1 '6 1.8
CONCENTRATION (M) FIGURE 8 MSASS + 18-C-6/WATER
33-S 1000/W VS CONCENTRATION 35 34 33 32 31 D 30 29 n 28 Ul E 27 \__) :;;. 26 0' 0 25 0 D ' 24 0 D D I 23 [' ' 22 21 D 20 19 18 17 16 15 0 0.2 0.4 0.6 0.8 1 1 2 1. 4 1.6 1.8 2
CONCENTRATION (M) 44 The fluorinated analog of methanesulfonic acid, trifluoromethanesulfonic acid (TFMSA) , was investigated to compare the effects of proton substitution on sulfur and oxygen linewidths and chemical shifts (Figures 9, 10 and 11) at ambient and elevated temperatures.
73 CF3 S03H is a superacid and tends toward autoionization. In general, the autoprotolysis of a superacid is represented by:
[12] where HA is the acid, H2A+ is the protonated acid and A- is the anionic form. On the Hammett scale, the acidity lies in the
H0 = -13 to -15 range - stronger than 100% sulfuric acid
(H2SOd. With this in mind, it is not surprising that the linewidths for 170 were narrower than those for methanesulfonic acid. In the presence of three equivalent oxygen atoms, the sulfur nucleus is tetrahedral. Figures 9 and 10 are the plots of 1000/~v~ versus concentration for TFMSA. 45
Table 11. Concentration dependence of 170 and 33S chemical shifts and linewidths of trifluoromethanesulfonic acid in water at T = 20±1°C. (* = resonance too broad for an accurate determination of chemical shift.)
______170------______33s------
Concentration/M .6.v.;/Hz 6/ppm .6.vli/Hz 6/ppm 11 400 143 4000 * 8.8 190 140 980 -27 7.0 130 144 700 -28 4.9 91 148 550 -25 3.3 68 151 360 -22 1. 7 56 154 264 -23 0.83 59 154 246 -24 0.41 59 155 200 -22 0.21 53 153 200 -23
Table 12. Concentration dependence of 170 and 33S chemical shifts and linewidths of trifluoromethanesulfonic acid in water at T = 50±1 ° C. ( * = resonance too broad for an accurate determination of chemical shift.)
______170------______33s------
Concentration/M .6.vli/Hz 6/ppm .6.vli/Hz 6/ppm 11 310 146 1700 * 8.8 135 141 580 -26 7.0 79 145 420 -25 4.9 54 149 350 -24 3.3 43 153 250 -24 1. 7 41 156 200 -23 0.83 37 157 184 -24 0.41 77 156 167 -23 0.21 47 155 150 -23 FIGURE g TRIFLUORO-MSA/WATER 17-0 1000/W VS CONCENTRATION 28 <) 26
24 <) <) 22
20 ~ n D <) lll E 18 D u D D ;;:: 16 '- 0 0 D 0 14 ' <) 0 I 12 f' ' D 10
8 D
6
4 <) 2 0 2 4 6 8 10 12
CONCENTRATION (M) D 20 C o SO C FIGURE 10. TRIFLUORO-MSA/WATER
33-S 1000/W VS CONCENTRATION 7
<)
6 <)
<)
5 DD <)
{\ tn E \_} D <) 3 '- 0 0 0 ' 3 If) <) I D (T) (T)
2 D
D
1
CONCENTRATION (M) D 20 C <> SO C FIGURE 11. TRIFLUORO-MSA/WATER 17-0 CHEMICAL SHIFT VS CONCENTRATION 156 155
15"1 D 153 D 152 n E 151 D Q Q v 150 f- 1"19 LL I 1"18 D If)
_J 1"17 <( u 1"16 2 w I 1"15 u 1"1"1 0 I [' 1"13 ' 1"12 1"11
1"10 D 139 138 0 2 "1 6 8
CONCENTRATION (M) 49
2. Alcohols Alcohols possess hydrogen bonding capabilities similar to those of water and are known to form linear polymers comprised of five to seven monomer units. 74 There is a high degree of organization in the bulk solvent. The concentrations of M8A in methanol and ethanol ranged from 3.1
M to 0.19 M. In both cases, the linewidths for 170 and 338 were greater than those observed for the aqueous solutions. The chemical shifts for 338 averaged approximately -7. 4 ppm (MeOH) and -9. 2 ppm (EtOH) - 2 to 4 ppm upfield from the 338 resonances in water. The 338 chemical shifts are considered averages (instead of absolute 6-values) because the lines were not well resolved. CH/70H linewidths and chemical shifts are reported in an attempt to correlate two hydrogen-bonding systems (water and methanol). 170 and 338 spectral data are given in the following Tables and Figures. Although it was possible to detect signals in ethanol, both the low signal to-noise and extremely long acquisition times made further experiments untenable. Therefore, emphasis was placed on those concentrations which approached infinite dilution. 50
Table 13. Concentration dependence of 170 chemical shifts and linewidths of methanesulfonic acid in methanol and ethanol. Methanol
Concentration/M .6.11lii/Hz 6/ppm
3.1 130 173 1.5 97 174 0.77 90 174 0.39 82 173 0.19 82 174
Ethanol
Concentration/M 6/ppm
1. 5 150 168 0.77 130 171 0.39 100 171 0.19 95 166
Table 14. Concentration dependence of 33S linewidths of methanesulfonic acid in methanol and ethanol. The extremely low signal-to-noise of the 33S lines prohibited an accurate determination of chemical shift.
Methanol
Concentration/M .6.vlii/Hz 6/ppm
3.1 210 -7.0 1. 5 100 -7.3 0.77 52 -7.4 0.39 36 -7.6 0.19 32 -7.8
Ethanol
Concentration/M .6.11lii/Hz 6/ppm
1. 5 450 -8.1 0.77 300 -10 0.39 240 -9.7 0.19 180 -9.0 FIGURE 12. METHANESULFONIC ACID/R-OH 17-0 1000/W VS CONCENTRATION
0 0 12
11 n D IJl E 0 u 10 ~ D :;;: '- 0 0 0 ' 9 0 I ['- ' 8 D
7 D
6 0 0.4 0.8 1 2 1.6 2 2 4 2.8 3.2
CONCENTRATION (M) D ETHANOL o METHANOL
U1 ......
53
Viscosity corrections (~v~/ry) to the linewidth yield an unexpected result. While the 338 linewidths follow the anticipated order, the 170 resonances in methanol were broader than those for ethanol. With a shorter alkyl chain, methanol is more water-like in nature and more prone to increased hydrogen bonding with the solute. The addition of a methylene group gives the solvent more micellar qualities. The viscosity corrected linewidths at infinite dilution are given in Table 15. 54
Table 15. 170 and 33S comparison of the viscosity non- corrected and viscosity corrected linewidths at infinite dilution for methanesulfonic acid in methanol and ethanol. Non-corrected Corrected Me OH EtOH Me OH EtOH ..6..11y'Hz ..6..11i,./Hz ..6..11i,./Hz ..6..11i,./Hz
79 145 34 163 92 85 183 170 55
3. Amides The linewidth dependence on concentration was observed for solutions of methanesulfonic acid in formamide (FAD), N methylformamide (NMF) and N,N-dimethylformamide (DMF). The extrapolated M8A linewidths at infinite dilution, without corrections for the effects of viscosity, indicated that the narrowest resonance was achieved in NMF. However, viscosity corrections indicated that the linewidth trend was as expected
- FAD < NMF < DMF. Figures 14 and 15 display the data in the usual format. 170 chemical shifts are reported in Table 16.
The relative simplicity of these solvents make the viscosity corrections straightforward. Table 18 is a comparison of the viscosity non-corrected viscosity and corrected viscosity linewidths for 170 and 338 at infinite dilution.
The 170 chemical shifts appear to be constant for FAD and
NMF while downfield shifts were observed in DMF. FAD and NMF possess a proton capable of hydrogen bonding. DMF, an aprotic solvent, exhibits a decrease in organization in the bulk liquid. The 338 chemical shifts remained constant for a given solvent over the entire concentration range: FAD (-6.1 ppm),
NMF (-7.8 ppm) and DMF (-9.0 ppm). 56
Table 16. Concentration dependence of 170 chemical shifts and linewidths of methanesulfonic acid in FAD, NMF and DMF. (* = no spectrum was observed in a "reasonable" number of transients.)
------FAD------NMF------DMF------C/M ~11\/Hz o/ppm ~11\/Hz o/ppm ~11\/Hz o/ppm
3.1 265 182 180 179 1.5 140 183 190 182 120 179 0.77 130 184 130 182 110 181 0.39 99 183 87 184 105 184 0.19 * * 98 184 100 185
Table 17. Concentration dependence of 338 chemical shifts and linewidths of methanesulfonic acid in FAD, NMF and DMF.
------FAD------NMF------DMF------C/M ~11\/Hz o/ppm ~11\/Hz o/ppm ~11\/Hz o/ppm
3.1 71 -6.0 560 -9.0 1. 5 32 -6.2 16 -7.7 38 -7.6 0.77 27 -5.9 19 -7.8 34 -9.1 0.39 27 -6.3 20 -7.8 31 -9.4 0.19 25 -6.2 14 -7.9 31 -9.8 0.096 16 -6.4
Table 18. 170 and 338 comparison of the viscosity non- corrected and viscosity corrected linewidths at infinite dilution for methanesulfonic acid in FAD, NMF and DMF. Linewidths reported in Hz.
Non-corrected Corrected
FAD NMF DMF FAD NMF DMF
98 84 97 26 51 121 21 16 27 6.0 10 34 FIGURE 14' METHANESULFONIC ACID/AMIDES 17-0 1000/W VS CONCENTRATION 12
(>
11
(> 10
9 n tn E u 3 8 '0 0 0 ' 7 0 I !"- ' 6 x
5
0 0.4 0.8 1.2 1 6 2 2.4 2.8 3.2
CONCENTRATION (M) 0 FORMAM I OE o N-METHYLFORMAM I DE X OIMETHYLFORMAMIDE
U1 -..J FIGURE 15. METHANESULFONIC ACID/AMIDES 33-S 1000/W VS CONCENTRATION 80 0
70
D <) 60
<) n (fl 50 0 E \_} 3: '0 0 40 D 0 D D ' If) x I [T] 30 [T] x
20
D 10
x 0 0 0.4 0.8 1 2 1.6 2 2.4 2.8 3 2
CONCENTRATION (M) D FORMAMIDE <) N-METHYLFORMAMIDE x DIMETHYLFORMAMIDE
(J1 00 59
4. Ethers A series of ethers were used as solvents (Figures 16 and 17). Two aprotic ethers (tetrahydrofuran THF and dimethoxyethane - DME) and one protic ether - methyl carbitol (CAR). The narrowest resonance was achieved in THF. Linewidths increased as the molecular weight of the ether increased. All three solvents possess extremely low
2 viscosities (mNsm- ): THF - 0.55, DME - 0.455 and CAR - 0.348. The viscosity corrected linewidths indicate that the resonances are significantly broader than were expected. The 33S resonance in CAR was too broad for detection (Table 20).
The 170 and 33S resonances in these solvents were not well resolved. In no case was a sharp line observed. The chemical shifts reported are therefore approximations. The center of the 33S chemical shifts in THF and DME were measured to be approximately: THF (-11 ppm), DME (-6.6 ppm). The signal-to noise of 170 resonances in THF was so low that an accurate determination of the chemical shift was impossible. 60
Table 19. Concentration dependence of 170 chemical shifts and linewidths of methanesulfonic acid in THF, DME and CAR. (* = signal-to-noise too low to ascertain chemical shifts; **=acquisition time prohibitive.)
------THF------DME------CAR------C/M t.11lii/Hz cS/ppm t.11lii/Hz cS/ppm t.11lii/Hz cS/ppm
3.1 220 * 320 160 740 178 1.5 140 * 210 172 550 174 0.77 110 * 260 176 460 175 0.39 110 * 210 177 440 175 0.19 ** ** 160 177 400 177
Table 20. Concentration dependence of 338 chemical shifts and linewidths of methanesulfonic acid in THF and DME. (*=acquisition times prohibitive.)
------THF------DME------Conc./M t.11Js/Hz cS/ppm t.11lii/Hz cS/ppm
3.1 870 -12 1500 -6.0 1. 5 335 -8.0 980 -14 0.77 510 -14 640 -7.2 0.39 240 -9.0 * * 0.19 335 -10 * *
Table 21. 170 and 338 comparison of the viscosity non- corrected and viscosity corrected linewidths at infinite dilution for methanesulfonic acid in THF, DME and CAR. Linewidths reported in Hz. (* = line too broad for detection)
Non-corrected Corrected
THF DME CAR THF DME CAR
100 183 404 182 402 1160 284 581 * 516 1280 * FIGURE 16 METHANESULFONIC ACID/ETHERS 17-0 1000/W VS CONCENTRATION
9 x x
8
7 x n (j) E \_) D 3 6 '0 0 0 ' 5 0 D D I I' ' 4 D
3
0
2
1 0 0 4 0.8 1 2 1.6 2 2.4 2.8 3 2
CONCENTRATION (MJ D DIMETHOXYETHANE 0 METHYLCARBITOL x TETRAHYDROFURAN
O'\ I-' FIGURE 17. METHANESULFONIC ACID/ETHERS 33-S 1000/W VS CONCENTRATION
<> 4
3.5
n (fl 3 E <> <> u 5 '- 0 0 2 s D ' If) I (T] 2 (T] <>
1.5 D
<> 1 D
0.5 0 0.4 0.8 1 2 1.6 2 2.4 2.8 3.2
CONCENTRATION (M) D DIMETHOXYETHANE <> TETRAHYDROFURAN 63
5. Acetonitrile
Acetonitrile (CH 3CN) is another example of an aprotic
2 solvent possessing low viscosity (0.345 mNsm- ) and a high dipole moment (3. 92 D). While the linewidths of the 170 resonances were relatively sharp (Figure 18), the 33S resonances were so broad (Figure 19) that accurate determinations of chemical shifts were not possible. The chemical shifts for 170 appear to be invariant with changes in concentration (Table 22). 64
Table 22. Concentration dependence of 170 and 33S chemical shifts and linewidths of methanesulfonic acid in acetonitrile. (* = signal-to-noise too low to determine chemical shift.)
______33 ______170------8 Conc./M t..v~/Hz 6/ppm t..v~/Hz 6/ppm 5.4 180 171 990 * 3.9 130 171 860 * 2.7 120 171 720 * 1. 9 100 171 690 * 0.96 87 171 590 * 0.48 80 172 550 * FIGURE 18. METHANESULFONIC ACID/CH3CN 17-0 1000/W VS CONCENTRATION 13
D 12
11
n lll 10 D E u 3 '- 0 0 9 0 ' 0 D I f" 8 ' D
7
6
D
5 0 2 6
CONCENTRATION (M) FIGURE 19. METHANESULFONIC ACIO/CH3CN
33-S 1000/W VS CONCENTRATION 1.9
1.8 0
1.7
1.6
"lf) E 1.5 u
~ D 0' 0 1.4 0 ' If) I 1.3 fTl fTl 1.2 D
1.1
1 D
0.9 0 2 4 6
CONCENTRATION (M) 67 6. Acetone and DMSO Methanesulfonic acid in acetone and DMSO revealed interesting results (Figures 20 and 21). The expected relationships between linewidth and concentration were observed for 170 in acetone and 33S in DMSO. However, the 170 lines in DMSO and the 33S lines in acetone displayed contradictory behavior - linewidths increased with decreasing concentration. The 33S linewidths in acetone increased so rapidly that below 0.39 M, they could not be measured. The signal-to-noise of the 33S resonances in acetone was too low to enable an accurate determination of the chemical shift. 68
17 33 Table 23. Concentration dependence of 0 and S chemical shifts and linewidths of methanesulfonic acid in acetone and DMSO. (* = line too broad for chemical shift determination; ** = line not observed.)
Acetone ______170------______33s------cone.JM Llv\JHz 6Jppm Llv\JHz 6Jppm 1.5 140 170 880 -7.6 0.77 99 173 1200 -9.3 0.39 81 180 3400 * 0.19 81 183 ** ** DMSO
______170------______33s------Cone.JM Llv\JHz 6Jppm Llv\JHz 6Jppm 3.1 165 181 45 -9.0 1. 5 175 181 59 -8.6 0.77 180 182 45 -8.9 0.39 180 182 39 -9.2 0.19 190 182 16 -9.3 FIGURE 20. MSA/ACETONE & DMSO
17-0 1000/W VS CONCENTRATION 13
D D 12
11
" 10 ~ u 3: 0' 0 9 0 ' 0 I 8 "'
7
6
0 0 5 0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2
CONCENTRATION (M) 0 ACETONE 0 DIMETHYLSULFOXIDE FIGURE 21 MSA/ACETONE & DMSO
33-S 1000/W VS CONCENTRATION Lj 0
35
30
n () Ul 25 E u 5 0 0 '- 0 0 20 0
' () If) I (T) 15 (T)
10
5
0 0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2
CONCENTRATION(M) D ACETONE () DMSO
-..J 0 71
Table 24. Summary of linewidths at infinite dilution and calculated spin-spin relaxation times for a) methanesulfonic acid in a variety of solvents, b) aqueous trifluoromethanesulfonic acid and c) aqueous methanesulfonic acid sodium salt with stoichiometric 18-crown-6. a) Methanesulfonic acid ______170------______33s------
Solvent li.viJHz T2/ms ti.v 31/Hz T2/ms Water coupled - 20°C 62 5.1 27 11 coupled - 40°C 57 5.6 25 13 decoupled - 40°C 53 6.1 22 14 Me OH 79 4.0 34 9.3 EtOH 92 3.5 183 1. 7
FAD 98 3.2 21 11 NMF 84 3.8 16 20 DMF 97 3.3 27 11
THF 100 3.2 284 1.1 DME 183 1. 7 581 0.55 CAR 404 0.8 ---too broad---
Acetone 74 4.3 8150 0.04 DMSO 187 1. 7 25 13
Acetonitrile 78 4.1 540 0.59 b) Trifluoromethanesulfonic acid
Water - 20°C 53 6.0 216 1.5 50°C 41 7.6 165 1. 9 c) Methanesulfonic acid sodium salt with stoichiometric amounts of 18-crown-6
Water - 20°C 71 4.5 31 10 CHAPTER V
DISCUSSION
Both protons and neutrons have a spin quantum number of
~. If the spins are paired, there will be no net spin and the
nuclear spin quantum number, I, will be zero. For a particle having I = ~, there is one unpaired spin which imparts a nuclear magnetic moment, µ, to the probe nucleus. This distribution of charge is spherical. For nuclei with I > ~, the charge distribution is non-spherical. These nuclei are termed quadrupolar. The orientation of charge is determined by the sign of the quadrupole moment. If eQ > O, the charge
is directed along the z-axis (prolate distribution of charge) ; eQ < O implies charge accumulation perpendicular to the z-axis
(oblate distribution of charge). Unpaired nuclear spins lead to a nuclear magnetic moment. The nuclear spin angular momentum quantum number, m1 , takes on the values I, I-1, .....
(-I+l), -I.
Circulating particles possess angular momentum defined by75
p(rp) = r x mv [13] where r is the position vector of the particle; v is the
72 73
linear momentum vector, m the mass and ~ the angular change
of the angular momentum. The angular momentum, p, is perpendicular to the plane of the circulating charge.
The NMR experiment is used to study the nuclear spin
orientation, in the rotating frame, with respect to the fixed laboratory frame. The rotating frame revolves at a frequency
• w1 which is proportional to the applied field, H1 The rotating and laboratory frames share a common z-axis. The Bloch equations define the change in magnetization
75 76 with time and the application of H1 • ' Used to describe the
processes of spin ~ systems, they provide a descriptive
foundation for the magnetic relaxation of all species. The
time dependence of the total magnetization, M(t), is given by:
d 1
M(t) = nµ 0 - M(t) + -yM(t) x H(t}. (14] dt nµ 0 describes the individual magnetization of n spins with µ 0 parallel to the z-axis. TR is the time required for the
system to return to equilibrium following a radio-frequency pulse. H (t) describes the precession of the nuclear spins about the total magnetic field where H0ez is the static field and H1 (t) is the applied field of frequency w:
[15]
In the presence of a static magnetic field, the magnetization vector is parallel to Oz. With the introduction of a radio-frequency pulse perpendicular to the z-axis, the 74 magnetization experiences a torque and is forced into precession about the z-axis with a constant angular velocity of w0 (proportional to the applied field) . This phenomenon is known as Larmor precession and w0 is the Larmor frequency
wo = --yBo. [16] The time-dependent magnetization is defined by three components which offer approximate solutions to [13]:
d
-Mz = nµ 0 - + i cos wt (M_ - M+) , [17] dt TR 2
d -~ [18] dt
~ are the raising and lowering magnetization operators given by
[19] They represent the x and y components of the rotating frame. w1 is the angular frequency of the applied field, --yB1 • It is the interaction of the ~ and Mz components which induce the torque. This theory provides the basis for Fourier transform
NMR (FT NMR) •
For nuclei with I > ~, the coupling of the electric field with a quadrupolar nucleus is, in tensor form, given by
[20]
The most significant contribution to the relaxation process being the interaction of Q, the nuclear quadrupole moment,
54 77 78 with the fluctuating electric field gradient, q. • • 75
The components of tensor A, Aij, in the laboratory frame, are linear combinations of the components in the molecular frame. 21 The tensor coupling can be rewritten
H1 = LmF(m) (rl) A (m) (I) [21] where p
Random processes (i.e., Brownian motion) in which one variable does not entirely depend on another are described using correlation functions and are written in terms of probabilities. The probabilities are proportional to the spectral density. The self-correlation of a variable is 76 expressed as an auto-correlation. Under conditions of extreme narrowing, the auto-correlation function
G(r) = F(t) ·F(t+r) [22] is given by the Fourier transform of the reduced correlation
21 22 function •
F(m) (t) F(m)* (t+r) [23]
I F(m) (t) I2
The Fourier transform of the auto-correlation function [22] gives the spectral density
~ ~ J(w) = 2 J G(r) cos(wr) dr =_J G(r) e~ 7 dr [24] and
2r c J(w) = with J(2w0 )=J(w0 )=J(0)=2rc. [25]
The linewidth is then defined as
2 1 1 3 21+3 2 = = l+i] (eQ dV] re. [26] 2 40 [ 3 Ii dz
T1 and T2 are the spin-lattice (longitudinal - along the z axis) and spin-spin (transverse - perpendicular to the z axis) relaxation times respectively. The electric field gradient, eq, is a molecular property and is dependent on the overall charge distribution, temperature and the effects of solvent molecules in the primary salvation sphere. It is defined as 77
2 d 2V/dz , the gradient along the z-axis. Q, the nuclear quadrupole moment, depends on the state of the nucleus and may be considered constant because nuclei are usually encountered in their ground electronic states. The quadrupolar coupling constant, e 2qQ, is assumed to be temperature-independent and can be evaluated by analysis of the hyperfine structure. T} is the electric field asymmetry parameter designated by
(qyy - 'Lex) T} = [27] qzz qij are the components of the symmetrical electric field tensor where I qzz I~ I 'Lex I ~ I qyy I and T} is between 0 and 1. A value of
21 T]=O implies axial symmetry of the nuclear surroundings.
Elements of the electric field tensor are not independent. The choice of molecular axes is arbitrary but the most convenient selection is one such that the trace of the diagonalized tensor matrix [12] is zero.
Tr = 0 [28]
This choice yields the axes of the principal axis system, the
conditions under which the Laplace equation The local field produced by the precession of the nuclear moment contains a fixed component in the z-direction and a fluctuating component to which it is orthogonal. Many 78 nuclei contribute to a local field and all will be affected bY local dipolar fields of their neighbors. The correlation time and linewidth are temperature, concentration and viscosity dependent. Sharper lines are obtained at higher temperatures with low viscosity solvents. Molecular tumbling decreases rapidly with increasing molecular radius, decreasing temperature and increasing viscosity. The rotational correlation time, Tc, is the time required for the lattice to return to its unperturbed state after a radio-frequency pulse. 69 The temperature-dependence of Tc is given by [29] The spin-lattice relaxation time for a spherical molecule in a continuous, homogeneous medium can be calculated21 using the Debye-Stokes-Einstein (DSE) relation where ~ is the solution viscosity, a is the molecular radius, 23 1 k is Boltzmann's constant ( 1. 381X10- JK- ) and T is temperature (OK) [30] Although the DSE equation predicts a linear relationship between T2 and viscosity, this phenomenon has not been observed in studies of 33S in the benzenesulfonate anion. 44 The Grier-Wirtz equation40 is a modification of the DSE relation and compares the correlation time to solvent and solute molecular diameters by the following expression where V is the molecular volume 79 T x=rsoluteVTJ/r solvent• [ 31] The concentration and solvent dependence of 170 and 33S linewidths and chemical shifts have been investigated using nuclear magnetic resonance. In general, linewidths are expected to decrease with decreasing solute concentration, increasing temperature, decreasing solution viscosity and decoupling. In 1970, Covington et al. 79 described the behavior of moderately strong acids in aqueous solutions. Using trifluoro- and trichloroacetic acids, they proposed that acid dissociation is a two-stage process: ionization and the subsequent dissociation of an ion pair. The protonated solvent and deprotonated solute molecules are in contact for a brief period prior to dissociation. It is this association than can account for some of the line-broadening and changes in chemical shift evident in the oxygen spectra. For some aqueous sulfonic acids, the process is represented by the following two-step equilibrium: The ion pair is held together by either hydrogen bonding or electrostatic forces. The strength of an acid is determined by its ability to transfer a proton to an adjacent solvent molecule. For strong acids such as MSA and TFMSA , K1 will dominate the overall equilibrium. However, as previously stated, TFMSA tends toward autoionization and may forego the 80 intermediate step. Generally, organic sulfonic acids are strong and ionized to the same extent as their corresponding salts because they are fully dissociated in solutions of low 80,81 p H • For this family of acids, the 3d orbitals of sulfur are contracted and allow more efficient ~so overlap with the 18 82 83 2P oxygen orbitals. ' ' In four-coordinate sulfur compounds, svr, the chemical shifts of terminal oxygen atoms are 18 39 rationalized by ~-bonding effects ' - they are shielded with respect to their bridging counterparts. As an example, Klemperer18 reported the following 170 chemical shift data: o = 167 ppm [32] 0 terminal = 15 0 ppm abridging = 102 ppm [33] Both 170 and 33S are quadrupolar nuclei possessing relatively small nuclear quadrupole moments. 42 If, in diamagnetic compounds, oxygen-17 is spin coupled to a nucleus possessing a quadrupole moment smaller than its own, the oxygen relaxation mechanism will dominate. 68 In order to achieve narrow linewidths, the electric field gradient should be as 18 84 85 small as possible. "Electronic symmetrization" • • has been observed in the conversion of a sulfenyl (-S-) to a sulfonyl 33 (-S02 ) sulfur. This reduces the linewidth of the S absorption. To date, sulfur-33 signals with "reasonable" linewidths (Hz vs kHz) are obtained in compounds with tetravalent sulfur atoms (except CS 2 ). The tetrahedral symmetry about the sulfur nucleus in so/- produces narrow 18 86 lines for the ion ' and sensitizes it to ion-ion and ion- 81 solvent interactions. In the system the interactions are assumed to be electrostatic. This has a pronounced effect on the efg at the sulfur atom. In MSA, the chemical environment of the sulfur is nearly symmetric. oxygen and sulfur chemical shifts are dominated by the paramagnetic term in the isotropic shielding constant (3]. The paramagnetic (ap) and diamagnetic (a0 ) terms are given by µ.o e2 3 ( O'o) = 3 µ.o e2 <0 I Lk'kN- /kN I n> O'p depends on all the molecular excited states, n~O. Qualitatively, a 0 depends on the "spherical" nature of the electronic distribution, while O'p is identically zero for a spherical electronic distribution and relies on electronic asymmetry. Although a 0 may be large, it does not change a great deal over a set of chemical compounds - it is always positive and zero only for a nucleus without electrons. Because the chemical shift ( c5k) (36] a ref is affected by changes in ak, it is relatively small for a0 82 beyond the first few elements of the periodic table. However, Gp causes downfield shifts as asymmetry increases. In some cases, Gp may cause shifts downfield from the bare nucleus. There are absolute shielding scales for both 170 and 87 88 335. • The absolute isotropic shielding is known for at least one compound containing these nuclei. Using this as a reference, the absolute shielding is obtainable for all other chemical species involving the nucleus in question. For nuclei with I=\, especially protons, high electron density shields the nucleus causing an upfield shift while low electron density deshields and induces a downfield shift. In this case, the paramagnetic contribution is zero. For nuclei with p and d-orbitals and I~\, high electron density deshields the nucleus and effects a downf ield shift whereas low electron density shields the nucleus inducing an upfield shift. Here, the paramagnetic term is generally a large observed value. The influence of the paramagnetic term can be seen in the chemical shift ranges for 170 and 335. Using a water reference, oxygen lines occur between o and 1600 ppm. 89 With C5 2 as a reference, most sulfur lines occur between approximately -300 and +400 ppm. As can be seen, the possible shifts for these nuclei are far greater than those expected for either 1H or 13C. Although the chemical shifts of the lines we observed do fall within these ranges, it is not possible to ascribe the shift to either a diamagnetic or 83 paramagnetic influence. The theoretical case in which one solute molecule is surrounded solely by solvent molecules is termed infinite dilution. This condition is approached but not achieved. It is at this "concentration" that the extrapolated linewidths and chemical shifts are characteristic of a single nucleus in a particular chemical environment. A change in solvent impacts the linewidth at infinite dilution by affecting the electric field gradient at the probe nucleus. Much of the data in this work is presented in plots of 1000/~v~ versus concentration where 1000 is a convenient scaling factor and ~v~ is the full width at half height (FWHH) of the resonant signal. Attempts have been made to correlate spectroscopic and spectrophotometric data with the physical constants of systems. However, it is not sufficient to know the intrinsic properties of pure systems as they do not take into account the interactions of various species. No correlations were observed in plots of solvent Y (Table 1), Z (Table 2) and ET values (Table 3) versus the spectroscopic data from these experiments. Water, methanol and formamide Y-values versus viscosity-corrected linewidths yielded a correlation of 0.56. z-values versus linewidths and viscosity-corrected linewidths gave correlations of 0.74 and 0.77 respectively. ET versus linewidths and viscosity-corrected linewidths provided correlations of 0.65 and 0.69 respectively. 84 Analyses of bulk solvent properties versus linewidth, inverse linewidth and chemical shift yielded no apparent correlation. In addition, there appeared to be no means of adequately predicting the order of solvents based on any set of data treatments. Partington90 has described the volume of solvent which has been influenced by a solute as the "cybotactic region" or the solvent cosphere of the solute. The solvent cosphere differs from the first coordination shell in that it represents the entire affected volume not merely the solvent molecules in direct contact with the solute. Because solvents possess characteristic molecular orientations over macroscopic distances, constants which describe specific systems (i.e., dielectric constants) cannot be used to describe the solvent in the cybotactic region. To circumvent this problem, extrapolated linewidths at infinite dilution were used as system models. Solvents which are capable of hydrogen bonding are termed protic. Water, formamide and NMF are highly associative solvents. This is evidenced in their unusually high dielectric constants. Associations of this type affect linewidths and chemical shifts. As previously stated, 170 and 33S possess broad chemical shift ranges. Changes in chemical shift are representative of either shielding, deshielding or an alteration of the nuclear environment. It is, therefore, helpful to recognize a chemical shift as characteristic of a 85 given functional group. This assists in the classification of various solvation phenomena. At higher aqueous MSA concentrations, broad resonances are observed for protonated acid molecules and acid aggregates. The similar response of the H/70 linewidths with decreased acid concentration is defined by equilibrium [10] and may be rationalized as follows: as the concentration of the protonated acid decreases, the concentration of the sulfonate decreases and we are nearing isolated solute ions surrounded by solvent molecules. Concurrently, as the concentration of the protonated solvent decreases, the H20 linewidth decreases. The degree of ionization versus inverse linewidth analyses proved linear over the entire concentration range. Consequently, it was not a suitable indicator for the presence of acid aggregates at low concentrations. Because of its tendency toward autoionization, TFMSA exhibits narrower 170 resonances that those measured for MSA. However, the presence of the larger fluorine atoms augment the asymmetrical environment about sulfur and broadens the resonances. A possible effect of the electronegative fluorines is exhibited in the changes in chemical shifts observed for both nuclei - the resonances for both 170 and 33S occur approximately 23 ppm upfield from MSA. Aqueous solutions of methanesulfonic acid sodium salt in the presence of 18-crown-6 confirmed the assumptions 86 initially made about the sulfonate system at infinite dilution. For sulfur, there was no significant line broadening associated with the presence of the sodium counter ion - the 33S linewidths are within 10% experimental error of the results obtained for MSA. Because 33S is a more sensitive probe for changes in molecular geometry, this indicated that no substantial ion-pairing was occurring at low concentrations. Because the complexation of sodium is an equilibrium process, the increase in the 170 linewidth was minimal. In the presence of strong acids, alcohols tend toward esterification and the formation of ethers. 91 100% sulfuric acid (PKa = -3, H0 = -13) drives the following reaction: 2ROH ~ ROR + H20. (37] The pKa and H0 -value for methanesulfonic acid has been reported as -0. 692 and -7. 9693 respectively. In solutions of methanol and ethanol, the degree of ether formation is unclear. The ethers of methanol and ethanol are aprotic and do not participate in hydrogen bonding with the acid. Esterification may be addressed in a number of ways. MSA is a strong hydrolyzing agent and the methyl esters are not expected to survive. However, the ethyl esters are not as easily hydrolyzed and the abrupt change in the 33S linewidth at infinite dilution between methanol and ethanol is representative of the formation of these ethyl acid esters: CH 3S03H + CH 3CH20H ~ CH3S02-0-CH2 CH3 + H20. [ 3 8] 87 This equilibrium is rapid and its residual effect is minimal linebroadening in the 170 spectra. Nonetheless, the decrease in symmetry about the 33S nucleus is sufficient to induce a broadening of the resonances. If either of these reactions occurred to an appreciable degree, the observation of H/70 resonances in the solution would have been observed and the necessity of an external reference would have not been necessary. In addition, the spectrum would have been complicated by the presence of additional 170 resonances. If the solutions contained considerable abundances of esters and ethers, the spectrum would reflect the presence of six types of oxygens - 1 MSA, 2 ester, 1 alcohol, 1 ether and 1 water. The ethers formed from methanol and ethanol are aprotic and analogous to THF and dimethoxyethane - the narrowest of the resonances (ether systems) occur in these solvents. Upon the addition of methyl carbitol (a protic and more complex solvent) the 33S resonances broaden to the extent that they cannot be detected. The extreme loss of symmetry in this hydrogen-bonded system reflect the sensitivity of sulfur linewidths to structural changes. The broadest 33S and 170 resonances were observed for solutions of MSA in THF, DME and CAR. With the exception of CAR, these represent aprotic solvents. Because of an apparent lack of solvent organization (a well-defined first solvation sphere), the solute molecules are more inclined to interact 88 and form acid aggregates. CAR is sizable in comparison to the other solvents. As exhibited by the enhanced 170 linewidth and an absence of a 338 resonance, it is the most strongly solvating system. With the exception of DMF, the dipolar aprotic solvents (acetonitrile, acetone and DM80) pose dichotomies. The increase in linewidth with decreasing concentration for the M8A solutions of 170/DM80 and 338/acetone could not have been predicted. While the M8A linewidths for 170/acetonitrile were relatively narrow, the 338 resonances were unusually broad. The correlations for both sets of data are on the order of 0.99. CONCLUSION Linewidth and chemical shift trends have been observed for natural abundance 170 and 33S in methanesulfonic acid within families of solvents, but, efforts to predict relaxation behavior in media possessing similar physical properties have not proven conclusive. No simple relationship has been found between solvent viscosity, density, dipole moment, donor number or acceptor number and 17 O and 33S linewidths and chemical shifts in solution. 33S and 170 exhibit immense chemical shift ranges. The sensitivity of these nuclei to changes in chemical environment (i.e., nuclear functionality and solvent) has been used in an effort to predict solvent effects on relaxation processes. 33S linewidths are extremely sensitive to the effects of changes in chemical environment. Solvents which prevent ion association should yield narrow 33S resonances. In agreement with the Berman and Stengle55 second class of solvents, the narrowest sulfur lines occurred in solvents of high dielectric constant and high Gutmann donor number: water, DMSO, DMF, FAD and NMF. There was no means of predicting the effect of these solvents on 170 linewidths. Aqueous solutions of trifluoromethanesulfonic acid 89 90 produced the expected results. The 170 linewidths decreased due to the autoionization of the acid and the 33S resonances broadened as a result of an increase in asymmetry about the sulfur nucleus. Due to shielding by the electronegative fluorines, the resonances for both nuclei were shifted approximately 23 ppm upfield from the parent compound. This confirms that changes in substituent may be used as a probe for substituent effects. Aqueous solutions of the sodium salt of methanesulfonic acid in the presence of 18-crown-6 verified that there was no significant degree of ion-pairing occurring in the lower concentration range. At 20°c, the 170 extrapolated linewidth at infinite dilution was found to be broader than that found for MSA/water. This is residual linebroadening due to the 170 in the crown ether. The extrapolated linewidth for 33S corresponded to that of methanesulfonic acid to within 10% experimental error. 17 33 Table 24 summarizes the 0 and S linewidths and T2 values for all solutes. As can be seen, there are linewidth trends within solvents of given functionalities, but, no correlation between functionalities. The narrowest resonances appear in highly associative solvents. Aprotic solvents are less capable of providing a well-defined salvation sphere and allow an higher degree of solute association. Using a variety of spectroscopic and spectrophotometric techniques, many researchers have investigated such systems 91 and devised limited scales upon which solvent behavior may be based (i.e., ET, Y and z-values). This work represents an alternative technique in the study of solvation phenomenon and provides a foundation upon which future NMR studies of these nuclei may be based. REFERENCES i. M. Filowitz, R. K. C. Ho, w. G. Klemperer, W. Shum, Inorg. Chem., 18, 1(1979). 2. H. T. Rall, C. J. Thompson, H. J. Coleman, R. L. Hopkins, American Petroleum Institute, RP60, Rept. 22, BU 659, 1972. 3. H. L. Retcofsky, R. A. Friedel, J. Amer. Chem. Soc., 9 4, 6579 ( 1972) . 4. G. Barbarella, C. Chatgilialoglu, s. Rossini, v. Tugnoli, J.Magn.Reson., 10, 204(1986). 5. (a) H. Takeuchi, H. Murata, I. Harada, J. Amer. Chem. Soc., 110, 392(1988), (b) R. C. Bethell, G. Lowe, Biochem., 27, 1125 ( 1988) , ( c) L. Einarsson, P. Westlund, J. Magn. Reson., 79, 54(1988), (d) Y. Shyy, T. Tsai, M. Tsai, J.Amer.Chem. Soc., 107, 3478 (1985), (e) J. A. Gerlt, M. A. Reynolds, P. C. Demou, G. L. Kenyon, J. Amer. Chem. Soc., 105, 6469 (1983). 6. K. Kosugi, T. Takeuchi, Org. Magn. Reson., 12, 435(1979). 7. c. T. G. Knight, A. R. Thompson, A. c. Kunwar, H. s. Gutowsky, E. Oldfield, R. J. Kirkpatrick, J. Chem. Soc. Dalton Trans., 275(1989). 8. L. P. Hammett, A. I. Deyrup, J. Amer. Chem. Soc., 54, 2721 ( 1932) . 9. G. S. Hartley, Aaueous Solutions of Para ff in Chain Sal ts, Hermann Press, Paris, 1936. 10. B. Halle, G. Carlstrom, J.Phys.Chem., 85, 2142(1981). 11. B. Lindman, NMR of Newly Accessible Nuclei, Vol. 1, Ch. 8, P. Laszlo, Ed., Academic Press, New York, 1983. 12. P. Mukerjee, J.ColloidSci., 19, 722(1964). 13. P. Ekwall, L. Mandell, P. Solyom, J. Colloid Interface Sci., 35, 519 ( 1971) . 14. D. E. Guvel i, J. B, Kayes, S. S. Dav is, J. Colloid Interface Sci., 72, 130(1979). 92 93 15. P. Mukerjee, J. R. Cardinal, N. R. Desi, Micellization, Solubilization and Microemulsions, Vol. 1, K. L. Mittal, Ed., Plenum Press, New York, 1977. 16. H. Uedaira, H. Uedaira, Bull.Chem.Soc.Jpn., 1265(1986). 17. R. Pottel, U. Kaatze, S. Muller, Ber. Bunsenges. Physik. Chem., 82, 1086(1978). 18. W. G. Klemperer, Angew.Chem.Int.Ed.Engl., 17, 246(1978). 19. C. Rodger, N. Sheppard, C. McFarlane, W. McFarlane, NMR and the Periodic Table, R. K. Harris and B. E. Mann, Eds., Ch. 12, Academic Press, New York, 1978. 20. J. Reuben, ].Amer.Chem.Soc., 91, 5725(1969). 21. A. Abragam, Principles of Nuclear Magnetism, Oxford University Press, London, 1961. 22. R. K. Harris, Nuclear Magnetic Resonance Spectroscopy, John Wiley and Sons, Inc., New York, 1986. 23. H. A. Christ, Helv.Phys.Acta., 33, 573(1960). 24. H. A. Christ, P. Diehl, H. R. Schneider, H. Dahn, Helv. Chim.Acta., 44, 865(1961). 25. S. Chimichi, R. Nesi, F. De Sia, Org. Magn. Reson., 22, 55 ( 1984) . 26. E. Block, A. A. Bazzi, J. B. Lambert, S. M. Wharry, K. K. Andersen, D. C. Dittmer, B. H. Patwardhan, D. J. H. Smith, J. Org. Chem., 45, 4807 ( 1980) . 27. J. c. Dyer, D. L. Harris, S. A. Evans, Jr., J. Org. Chem., 47, 3660(1982). 28. P. Balakrishnan, A. L. Baumstark, D. W. Boykin, Org. Magn. Reson., 22, 753 (1984). 29. D. W. Boykin, A. L. Baumstark, Tetrahedron, 45, 3613 ( 1987) • 30. A. L. Baumstark, M. Dotrong, M. G. Oakley, R. R. Stark, D. W. Boykin, J. Org. Chem., 52, 3640(1987). 31. S. Chang, W. J. le Noble, ].Amer.Chem.Soc., 105, 3708(1983). 32. Y. Masuda, M. Sano, H. Yamatera, J. Chem. Soc., Faraday Trans. I, 81, 127 (1985). 94 33. W. C. Copenhafer, P. H. Rieger, J. Amer. Chem. Soc., 100, 3776(1978). 34. J. A. Jackson, H. Taube, I.Phys.Chem., 69, 1844(1965). 35. J. F. Hinton, Annual Reports on NMR Spectroscopy, G. A. Webb, Ed., Vol. 19, Academic Press, New York, 1987. 3 6. H. Duddeck, U. Korek, D. Rosenbaum, M agn. Reson. Chem., 2 4 , 792 (1986). 37. A. -M. Hakkinen, P. Ruostesuo, Magn. Reson. Chem., 23, 424 (1985). 38. s. A. Evans, Maanetic Resonance. Introduction, Advanced Topics and APPlications to Fossil Energy, NATO ASI Series, L. Petrakis and J.P. Fraissard, Eds., D. Reidel Publishing Co., Boston, 1983. 39. P. S. Belton, I. J. Cox, R. K. Harris, J.Chem.Soc.,Faraday Trans., 2., 81, 63 ( 1985) . 40. R. Faure, E. J. Vincent, J. M. Ruiz, L. Lena, Org. Magn. Reson., 15, 401(1981). 41. D. L. Harris, S. A. Evans, Jr., J. Org. Chem., 47, 3358 (1982). 42. R. Annunziata, G. Barbarella, Org. Magn. Reson., 22, 250(1984). 43. D. S. Crumrine, B. Gillece-Castro, J. Org. Chem., SO, 4408 (1985). 44. D. C. French, D.S. Crumrine, J.Magn.Reson., 84, 548(1989). 45. N. s. Isaacs, Physical Oraanic Chemistry, Longman Scientific and Technical, Essex, England, 1987. 46. V. Gutmann, U. Mayer, Monatsch., 100, 2048(1969). 47. V. Gutmann, Chem.Brit., 1, 102(1971). 48. V. Gutmann, R. Schmidt, Coard. Chem. Rev., 12, 263 (1974). 49. V. Gutmann, Electrochem. Acta, 21, 661(1976). 50. C. Deverell, Prog.Nucl.Magn.ResonSpec., 4, 235(1969). 51. c. Deverell, Mo/. Phys., 16, 491(1969). 95 52. H. G. Hertz, Ber.Bunsenges.Physik.Chem., 77, 531(1977). 53. H. G. Hertz, Ber.Bunsenges.Physik.Chem., 9, 688(1973). 54. H. Weingartner, H. G. Hertz, Ber. Bunsenges, Physik. Chem., 81, 1204 (1977). 55. H. A. Berman, T. R. Stengle, I.Phys.Chem., 79, 1001(1975). 56. D. Lankhorst, J. Schriever, J. C. Leyte, Ber. Bunsenges. Physik. Chem., 86, 215(1982). 57. B. Halle, L. Piculell, J.Chem.Soc.,FaradayTrans.l, 78, 255(1982). 58. C. K. Finter, H. G. Hertz, J.Chem.Soc.,FaradayTrans.l, 84, 2735 (1988). 59. H. Weingartner, M. Holz, H. G. Hertz, J. Soln. Chem. , 7, 689 (1978). 60. M. Holz, H. Weingartner, H. G. Hertz, J. Soln. Chem. , 7, 705 (1978). 61. J. W. Akitt, Prog.NMRSpec., 21, 1(1989). 62. E. Grunwald, S. Winstein, I.Amer.Chem.Soc., 70, 846(1948). 63. S. Winstein, E. Grunwald, H. W. Jones, I.Amer.Chem.Soc., 73, 2700 (1951). 64. E. M. Kosower, I.Amer.Chem.Soc., 80, 3253(1958). 65. G. S. Reddy, J. H. Goldstein, J.Mol.Spec., 8, 475(1962). 66. K. Dimroth, C. Reichardt, T. Siepmann, F. Bohlmann, Ann., 661, 1(1963). 67. A. J. Shaka, J. Keeler, R. Freeman, J. Magn. Reson., 53, 313(1983). 68. J. Mason, Multinuclear NMR, J. Mason, Ed., Plenum Press, New York, 1987. 69. T. c. Farrar, B. M. Trost, s. L. Tang, s. E. Springer Wilson, J. Amer. Chem. Soc., 107, 1(1985). 70. A. K. Covington, R. Thompson, J.Soln.Chem., 3, 603(1974). 96 71. J. P. Kintz inger, J. M. Lehn, J. Amer. Chem. Soc., 9 6, 3313(1974). 72. A. Cornelis, P. Laszlo, C. Cambillau, J. Chem. Research, (S), 462 (1978). 73. R. Jost, J. Sommer, Rev. Chem. Intermediates, 9, 171(1988). 74. E. M. Kosower, An Introduction of Physical Orqanic Chemistry, John Wiley and Sons, Inc., N. Y., 1968. 75. R. S. Drago, Physical Methods in Chemistry, W. B. Saunders Co., Philadelphia, 1977. 76. C. Cohen-Tannoudji, B. Diu, F. Laloe, Quantum Mechanics, John Wiley and Sons, New York, 1977. 77. P. S. Hubbard, J. Chem. Phys., 53, 985 ( 1970) . 78. P. S. Belton, I. J. Cox, R. K. Harris, Magn.Reson,Chem., 24, 171(1986). 79. A. K. Covington, J. G. Freeman, T. H. Lilley, J.Phys.Chem., 74, 3773(1970). 80. L. Cassidei, O. Sciacovelli, J.Magn.Reson., 62, 529(1985). 81. Y. Kosugi, T. Takeuchi, Org.Magn.Reson., 12, 435(1979). 82. J. W. Kelly, S. A. Evans, Jr., Magn. Reson. Chem., 25, 305(1987). 83. J.C. Dyer, D. L. Harris, S. A. Evans, Jr., J.Org.Chem., 47, 3770 (1982). 84. P. s. Belton, J. D. Woollins, M agn. Reson, Chem., 24, 1080(1986). 85. D. L. Harris, s. A. Evans, Jr• I J. Org. Chem., 47, 3355(1982). 86. J. F. Hinton, D. Shungu, J. Magn. Reson., 54, 309 (1983). 87. R. E. Wasylishen, s. Mooibroek, J. B. Macdonald, J.Chem. Phys., 81, 1057 ( 1984) . 88. R. E. Wasylishen, C. Connor, J. O. Friedrich, Can.J.Chem., 62, 981(1984). 89. C. Brevard, P. Granger, Handbook of High Resolution Multinuclear NMR, John Wiley and Sons, New York, 1981. 97 90. J. R. Partington, An Advanced Treatise on Physical Chemistry, Vol. 2, Longmans, Green and Co., London, 1951. 91. J. March, Advanced Organic Chemistry, 3rd Edition, John Wiley and Sons, New York, 1985. 92. F. G. Bordwell, Acc. Chem. Res., 21, 456(1988). 93. R. C. Paul, v. P. Kapila, R. Kumar, S. K. Sharma, J.Inorg. Nucl. Chem., 43, 171(1981). APPENDIX A 99 APPENDIX A The following are the Lotus 1-2-3 regression data analyses. The best fit lines were calculated using the equation y = ax + b where a is the slope of the line and b is the intercept. All experiments were conducted at 20°C±l°C unless otherwise indicated. Linewidths are reported in Hz and inverse linewidths in ms (miliseconds). 100 1. Methanesulfonic acid in water; linewidth analyses. a. 2o·c Coupled ---~------11 ______0 33s------cone.JM t.i.v"!f. lOOOJ t.i.v"!f. Regressn. t.i.v\ lOOOJ t.i.v\ Regressn. 14 710 1.408450 2700 0.370370 11 430 2.325581 1000 1.000000 7.7 200 5.000000 4.671440 180 5.555555 4.776610 6.9 200 5.000000 5.849892 130 7.692307 8.064717 5.4 120 8.333333 8.059491 74 13.51351 14.22991 3.9 96 10.41666 10.26908 53 18.86792 20.39511 2.7 80 12.50000 12.03676 38 26.31578 25.32727 1.9 77 12.98701 13.21522 33 30.30303 28.61538 0.96 65 15.38461 14.59990 32 31. 25000 32.47890 0.48 67 14.92537 15.30697 25 40.00000 34.45177 0.24 64 15.62500 15.66050 28 35.71428 35.43820 0.19 66 15.15151 15.73416 33 30.30303 35.64370 0.15 63 15.87301 15.79308 28 35.71428 35.80811 Constant (b) 16.01404 36.42463 Std. Err. of y Est. 0.505769 2.755141 Corr. Coeff. 0.993331 0.975274 Slope -1.47306 -4.11013 b. 4o·c Coupled ______11 ______33s------0 Cone.JM t.i.v\ lOOOJ t.i.v\ Regressn. !::,.v\ lOOOJ !::,.v\ Regressn. 14 370 2.702702 1400 0.714285 11 240 4.166666 600 1.666666 7.7 120 8.333333 8.907857 130 7.692307 4.898760 6.9 100 10.00000 9.800325 140 7.142857 8.617099 5.4 94 10.63829 11. 4 7370 66 15.15151 15.58898 3.9 71 14.08450 13.14708 42 23.80952 22.56087 2.7 62 16.12903 14.48578 46 21.73913 28.13838 1.9 67 14.92537 15.37825 28 35.71428 31.85672 0.96 57 17.54385 16.42690 33 30.30303 36.22576 0.48 64 15.62500 16.96238 24 41. 66666 38.45677 0.24 58 17.24137 17.23012 27 37.03703 39.57227 0.19 58 17.24137 17.28590 25 40.00000 39.80467 0.15 60 16.66666 17.33052 22 45.45454 39.99058 Constant (b) 17.49786 40.68777 Std. Err. of y Est. 0.962115 4.072423 Corr. Coeff. 0.960033 0.958826 Slope -1.11558 -4.64792 101 c. 40°C Decoupled ______170------____ 33s------cone.JM l::i. v ':f. lOOOJ l::i.vis Regressn. l::i. v ':f. lOOOJ l::i.vis Regressn. 14 326 3.067484 1100 0.909090 11 184 5.434782 390 2.564102 7.7 110 9.090909 9.651810 96 10.41666 8.391661 6.9 96 10.41666 10.63477 160 6.250000 12.07899 5.4 85 11.76470 12.47783 47 21. 27659 18.99273 3.9 60 16.66666 14.32090 29 34.48275 25.90648 2.7 59 16.94915 15.79535 35 28.57142 31.43747 1.9 62 16.12903 16.77831 31 32.25806 35.12480 0.96 58 17.24137 17.93330 32 31.25000 39.45742 0.48 59 16.94915 18.52308 25 40.00000 41. 66982 0.24 55 18.18181 18.81797 27 37.03703 42.77602 0.19 54 18.51851 18.87941 24 41. 66666 43.00647 0.15 48 20.83333 18.92855 17 58.82352 43.19084 Constant (b) 19.11286 43.88221 Std. Err. of y Est. 1. 301508 7.322269 Corr. Coeff. 0.941465 0.880998 Slope -1.22870 -4.60916 7 2. Methanesulfonic acid in water; H/ 0 linewidth analysis. 17 ------H2 0------MSA Cone.JM l::i.v':f. lOOOJ l::i.vis Regressn. 14 490 2.040816 11 360 2.777777 7.7 160 6.250000 5.960174 6.9 190 5.263157 7.180754 5.4 97 10.30927 9.469340 3.9 78 12.82051 11. 75792 2.7 69 14.49275 13.58879 1.9 68 14.70588 14.80937 0.96 59 16.94915 16.24355 0.48 60 16.666666 16.97590 0.24 68 14.70588 17.34207 0.19 57 17.54385 17.41836 0.15 54 18.51851 17.47939 Constant (b) 17.70825 Std. Err. of y Est. 1. 293666 Corr. Coeff. 0.961291 Slope -1. 52572 102 3. Methanesulfonic acid in water; 17 o chemical shift analyses. ---2o·c Coupled------40°c Coupled---- Chem. Chem. Conc./M Shift Regressn. Shift Regressn. 7.7 163 163.9213 165 164.4474 6.9 166 165.2334 166 165.7775 5.4 168 167.6937 167 168.2713 3.9 170 170.1540 171 170.7652 2.7 172 172.1222 173 172.7603 1. 9 174 173.4344 174 174.0903 0.96 175 174.9762 175 175.6531 0.48 176 175.7634 177 176.4511 0.24 176 176.1571 177 176.8502 0.19 176 176.2391 177 176.9333 0.15 176 176.3047 177 176.9998 Constant (b) 176.5507 177.2492 Std. Err. of y Est. 0.485340 0.562395 Corr. Coeff. 0.995034 0.993525 Slope -1.64019 -1.66256 --4o·c Decoupled--- Chem. Conc./M Shift Regressn. 7.7 165 164.7662 6.9 166 166.0888 5.4 168 168.5686 3.9 171 171. 0484 2.7 174 173.0323 1.9 174 174.3549 0.96 176 175.9089 0.48 177 176.7024 0.24 177 177.0992 0.19 177 177.1818 0.15 177 177.2480 Constant (b) 177.4960 Std. Err. of y Est. 0.428414 Corr. Coeff. 0.996185 Slope -1. 65321 103 4. Methanesulfonic acid in water; degree of ionization versus inverse linewidth analyses. ______17 o------______33s------MSA Alpha Conc./M Est. 1000/ t::,.v\ Regressn. 1000//:::,.v\ Regressn. 14 0.509293 1. 408450 0.370370 11 0.646556 2.325581 1.000000 7.7 0.776962 5.000000 0.790486 5.555555 0.795246 6.9 0.807064 5.000000 0.790486 7.692307 0.812192 5.4 0.861915 8.333333 0.867066 13.51351 0.858360 3.9 0.914691 10.41666 0.914929 18.86792 0.900827 2.7 0.955419 12.50000 0.962792 26.31578 0.959897 1.9 0.981834 12.98701 0.973981 30.30303 0.991520 0.96 1. 012117 15.38461 1.029064 31.25000 0.999031 0.48 1.027266 14.92537 1.018513 40.00000 1.068428 0.24 1.034761 15.62500 1. 034587 35.71428 1. 034437 0.19 1.036316 15.15151 1. 023709 30.30303 0.991520 0.15 1. 037558 15.87301 1. 040285 35.71428 1. 034437 Constant (b) 0.675615 0.751184 Std. Err. of y Est. 0.011208 0.022512 Corr. Coeff. 0.993873 0.975046 Slope 0.022975 0.007931 104 5. Methanesulfonic acid sodium salt/18-C-6 in water; linewidth analyses. ______170------______33s------ Cone.JM !::. v \ 1000/ !::.v\ Regressn. !::. v it 1000/ !::.v\ Regressn. 1.9 141 7.092198 6.832543 47 21.27659 20.77758 1.6 123 8.130081 7.988703 43 23.25581 22.55457 1.4 105 9.523809 8.759476 43 23.25581 23.73923 1.1 108 9.259259 9.915636 39 25.64102 25.51622 0.92 102 9.803921 10.60933 41 24.39024 26.58241 0.36 85 11. 764 70 12.76749 32 31. 25000 29.89946 0.10 76 13.15789 13.76950 0.05 63 15.87301 13.96219 Constant (b) 14.15488 32.03185 Std. Err. of y Est. 1. 063172 1.380180 Corr. Coeff. 0.968444 0.933948 Slope -3.85386 -5.92329 105 6. Trifluoromethanesulfonic acid in water; 170 linewidth analyses. ------2o·c------5o·c------conc./M Li II\ 1000/ Li1111 Reg. Ana. fi II\ 1000/ Liv 11 Regressn. 11 400 2.500000 2.180020 310 3.225806 5.416678 8.8 190 5.263157 5.511783 135 7.407407 9.104310 7.0 130 7.692307 8.237772 79 12.65822 12.12146 4.9 91 10.98901 11. 41809 54 18.51851 15.64147 3.3 68 14.70588 13.84119 43 23.25581 18.32339 1. 7 56 17.85714 16.26429 41 24.39024 21. 00530 0.83 59 16.94915 17.58185 37 27.02702 22.46359 0.41 59 16.94915 18.21791 77 12.98701 23.16759 0.21 53 18.86792 18.52080 47 21. 27659 23.50283 Constant (b) 18.83883 23.85483 Std. Err. of y Est. 0.930535 5.091405 Corr. Coeff. 0.989545 0.811350 Slope -1. 51443 -1.67619 7. Trifluoromethanesulfonic acid in water; 33s linewidth analyses. ------2o·c------5o·c------Conc./M Li II\ 1000/ Liv 11 Regressn. Liv 11 1000/ Liv 11 Regressn. 11 4000 0.250000 -0.13376 1700 0.588235 0.346030 8.8 980 1. 020408 0.818971 580 1. 724137 1.485824 7.0 700 1.428571 1. 598479 420 2.380952 2.418383 4.9 550 1. 818181 2.507905 350 2.857142 3.506368 3.3 360 2.777777 3.200801 250 4.000000 4.335309 1. 7 264 3.787878 3.893698 200 5.000000 5.164250 0.83 246 4.065040 4.270460 184 5.434782 5.614987 0.41 200 5.000000 4.452345 167 5.988023 5.832584 0.21 200 5.000000 4.538957 150 6.666666 5.936202 Constant (b) 4.629900 6.045000 Std. Err. of y Est. 0.453126 0.425604 Corr. Coeff. 0.970555 0.981540 Slope -0.43306 -0.51808 106 8. Trifluoromethanesulfonic acid in water; 170 chemical shift analysis. Chem. conc./M Shift Regressn. 8.8 140 140.9642 7.0 144 143.9310 4.9 148 147.3923 3.3 151 150.0295 1. 7 154 152.6667 0.83 154 154.1006 0.41 155 154.7929 0.21 153 155.1225 Constant (b) 155.4687 Std. Err. of y Est. 1.195935 Corr. Coeff. 0.979039 Slope -1.64823 107 9. Methanesulfonic acid in MeOH; linewidth analyses. ______170------______33s------Conc./M /). v ls. 1000/ f).v\ Regressn. /).v\ 1000/ f).v\ Regressn. 3.1 130 7.692307 7.702039 210 4.761904 1.651609 1.5 98 10.30927 10.21391 100 10.00000 15.85264 0.77 90 11.11111 11.35995 52 19.23076 22.33186 0.39 82 12.19512 11.95652 36 27.77777 25.70460 0.19 82 12.19512 12.27050 32 31. 25000 27.47973 Constant (b) 12.56879 29.16610 Std. Err. of y Est. 0.211127 4.900919 corr. Coeff. 0.995156 0.926682 Slope -1.56992 -8.87564 10. Methanesulfonic acid in EtOH; linewidth analyses. ______170------______33s------Conc./M /).vi,. 1000/ f).vi,. Regressn. /). v ls. 1000/ f).vls. Regressn. 1. 5 150 6.666666 6.325229 450 2.222222 2.005228 0.77 130 7.692307 8.559276 300 3.333333 3.686977 0.39 100 10.00000 9.722205 240 4.166666 4.562409 0.19 95 10.58201 10.33427 180 5.555555 5.023162 Constant (b) 10.91573 5.460878 Std. Err. of y Est. 0.709492 0.553265 Corr. Coeff. 0.950253 0.946902 Slope -3.06033 -2.30376 108 11. Methanesulfonic acid in formamide; linewidth analyses. ______u ______aas------0 Conc./M ~v \ 1000/~v\ Regressn. ~v\ 1000/~v\ Regressn. 3.1 265 3.773584 3.685692 71 14.08450 12.57408 1.5 140 7.142857 7.051232 32 31. 25000 31.24084 0.77 130 7.692307 8.586759 27 37.03703 39. 75755 0.39 99 10.10101 9.386075 27 37.03703 44.19090 0.19 25 40.00000 46.52425 0.096 16 62.50000 47.62092 constant (b) 10.20642 48.74093 Std. Err. of y Est. 0.814646 9.011288 Corr. Coeff. 0.966920 0.856270 Slope -2.10346 -11.6667 12. Methanesulfonic acid in NMF; linewidth analyses. ______11 ______aas------0 Conc./M ~v\ 1000/~v\ Regressn. ~v\ 1000/~v\ Regressn. 1. 5 190 5.263157 5.159314 16 62.50000 57.30829 0.77 130 7.692307 8.422989 19 52.63157 60.27962 0.39 87 11.56069 10.12188 20 50.00000 61.82633 0.19 98 10.20408 11.01604 13 76.92307 62.64040 Constant (b) 11.86549 63.41375 Std. Err. of y Est. 1. 279477 14.65099 Corr. Coeff. 0.926988 0.192805 Slope -4.47078 -4.07030 13. Methanesulfonic acid in DMF; linewidth analyses. ______11 ______aas------0 Conc./M ~v\ 1000/~v\ Regressn. ~v\ 1000/~v\ Regressn. 3.1 180 5.555555 5.669422 560 1.785714 4.191999 1. 5 120 8.333333 8.041191 38 26.31578 21.12509 0.77 110 9.090909 9.123310 34 29.41176 28.85081 0.39 105 9.523809 9.686605 31 32.25806 32.87242 0.19 100 10.00000 9.983076 31 32.25806 34.98906 Constant (b) 10.26472 36.99986 Std. Err. of y Est. 0.205062 3.691611 Corr. Coeff. 0.994877 o.968710 Slope -1. 48235 -10.5831 109 14. Methanesulfonic acid in THF; linewidth analyses. ______170------______338------cone.JM /::,.1,1 lr. lOOOJ !::,.vlr. Regressn. /::,.vlr. lOOOJ t:,.vlr. Regressn. 3.1 220 4.545454 4.516787 870 1.149425 1. 268183 1. 5 140 7.142857 7.360879 335 2.985074 2.425227 0.77 110 9.090909 8.658495 510 1.960784 2.953129 0.39 110 9.090909 9.333967 240 4.166666 3.227927 0.19 335 2.985074 3.372557 Constant (b) 10.02721 3.509956 Std. Err. of y Est. 0.383675 0.883865 Corr. Coeff. 0.989364 0.744125 Slope -1. 77755 -0.72315 15. Methanesulfonic acid in DME; linewidth analyses. ______170------______33s------Cone.JM /::,.vlr. 1000Jt:,.vlr. Regressn. /::,.vlr. lOOOJt:,.vlr. Regressn. 3.1 320 3.125000 3.096048 1500 0.666666 0.614488 1. 5 210 4.761904 4.313174 980 1. 020408 1.186950 0.77 260 3.846153 4.868488 640 1. 562500 1. 448136 0.39 210 4.761904 5.157555 0.19 160 6.250000 5.309696 Constant (b) 5.454229 1.723633 Std. Err. of y Est. 0.873322 0.208647 Corr. Coeff. 0.764478 0.945025 Slope -0.76070 -0.35778 110 16. Methanesulfonic acid in CAR; linewidth analysis. ______110------cone.JM ~v\ 1000/~v\ Regressn. 3.1 740 1. 351351 1. 306544 1.5 550 1. 818181 -0.47565 0.77 460 2.173913 0.682765 0.39 440 2.272727 4.853660 0.19 400 2.500000 2.928706 Constant ( b) 2.469759 Std. Err. of y Est. 0.087192 Corr. Coeff. 0.985745 Slope -0.37523 The lines for 33S were too broad for detection. 111 17. Methanesulfonic acid in acetonitrile; linewidth analyses. ______170------______33s------cone.JM !:iv\ lOOOJ !:iv\ Regressn. !:iv\ lOOOJ !:iv\ Regressn. 5.4 180 5.555555 5.369576 990 1.010101 0.957811 3.9 130 7.692307 7.423327 860 1.162790 1. 202004 2.7 120 8.333333 9.066327 720 1.388888 1. 397358 1. 9 100 10.00000 10.16166 690 1.449275 1. 527594 0.96 87 11.49425 11.44867 590 1.694915 1. 680621 0.48 80 12.50000 12.10587 550 1. 818181 1. 758763 Constant (b) 12.76307 1. 836904 Std. Err. of y Est. 0.454907 0.059607 Corr. Coeff. 0.987408 0.984768 Slope -1. 36916 -0.16279 18. Methanesulfonic acid in acetone; linewidth analyses. ______170------______33s------Cone.JM flv\ lOOOJ!:iv\ Regressn. !:iv\ lOOOJt:iv\ Regressn. 1. 5 140 7.142857 7.157182 880 1.136363 1.191784 0.77 99 10.10101 10.24090 1200 0.833333 0.671445 0.39 81 12.34567 11.84613 3400 0.294117 0.400584 0.19 81 12.34567 12.69099 Constant (b) 13.49360 0.122594 Std. Err. of y Est. 0.440772 0.201529 Corr. Coeff. 0.989292 0.942433 Slope -4.22428 0.712793 19. Methanesulfonic acid in DMSO; linewidth analyses. ______170------______33s------Cone.JM flv\ lOOOJ!:iv\ Regressn. !:iv\ lOOOJt:iv\ Regressn. 3.1 165 6.060606 6.078513 45 22.22222 14.57104 1. 5 175 5.714285 5.702654 59 16.94915 27.41785 0.77 180 5.555555 5.531169 45 22.22222 33.27921 0.39 180 5.555555 5.441902 39 25.64102 36.33032 0.19 190 5.263157 5.394920 16 62.50000 37.93617 Constant (b) 5.350287 39.46173 Std. Err. of y Est. 0.102190 18.33060 Corr. Coeff. 0.952554 0.512185 Slope 0.234911 -8.02925 APPENDIX B 1. 6.9 M Methanesulfonic acid in water - 170 at 20±1°C (coupled). I i :· 1: ,.ft ' :I :i' t: ;\ :1 ;.. .. i! I~ ,, j! ",. I• '.i ,1 I :I II I! / j! I' I I I \ 11' Jj \ I I I I I ~LI I I I l I I ' I I I i' I I I I I ' I I I i 60J -~Ju -400 i',.>).I 2. 0.24 M Methanesulfonic acid in water - 33s at 20±1°C (coupled). 3. 0.96 M Methanesulfonic acid in water - 170 at 40±1°C (coupled). i\ 30000 20 'o·o 10000 0 -10000 HZ i ..I ~ I I I ·- 1~<;>.~2.l'f-' 6V•ji.."' 10·~ (~ :..51 Ht. I 14'> .'!> I I I I I I I I I' I r' ! I ( ; J ...=.---~"~ 141-,.;;...... ,.. ! !'. ,N I'II I 600 7200 7000 l ) 600 400 200 0 -200 -400 PPM 4. 0.77 M Methanesulfonic acid in water - 33s at 40±1°C (coupled). --,-----;--,-,---ir-.--,--.-.~,...--,--,---,,---,...--,--,·--,ri~,...--,--,---,~.,..-..,---,-~~r--l-.~.,..-~-,-~~r--rl-4--,-~~~l.-.--.~~~~-,--.~~.-.--r- 2060 -2000 -4000 ·6000 HZ 100 50 0 ...... (j\ 5. 0.96 M Methanesulfonic acid in water - 170 at 40±1°C (decoupled). 30000 20 0 10000 Q -10000 HZ I I .I I ~I llf "f J I ~ \~.;__..., I " t;J~ 1' / •' .. I 'I 1. 7600 7400 7200 7000 6800 6600 HZ i! ~~----~~~--~--~-....---....~...------...-.....1...._.._._., __ ~~·""J' ...... ___,,.._~~--,,,_--~~~~~~~~~~ 600 400 200 0 -200 -400 PPM ...... -...J 6. 7.7 M Methanesulfonic acid in water - 33s at 40±1°C (decoupled). 2000 d -2000 ·6 00 IC 100 50 0 I-' I-' OJ 17 7. 1.5 M Methanesulfonic acid in methanol 0 at 20±1°c. lO 20000 :odoo I '.0000 ·, __ ~7 l•t ! \ "II . . ' 11 ~~·--:'-~~"':-;\~----~--+--.\--!,'---,,--~~--->---- I v-1 " \/ ' -' ... , -.-J '\,..' ·,\ ' ,...... \ / ·,...... , I~ ...... , •) > 'I \ '-\ ---r--1---1- -...- -T-- ;·---, -- T---:-· r---,--· ;----·r----~ ---;----1~-----r--r--~T--~jJ --,--- :·soo . ~ooo 6500 5000 ,.,: r· --r -~ ·r·--: --!·-·1---1--r ·-·· ·-1-1 T-; ---: -- r-- ·: -1-j ··-r--r- r-rT ·-r-T r -~ -;- -r--;-- ~--i -~ --r-T- :·--:------:- r 600 400 200 -200 - ,100 ""'~' 8. 0.39 M Methanesulfonic acid in methanol - 33s at 20±1°C. ! -. -·--1· r -·r-:· ---r-- -- -: ·--:--·-1··1-···r-1····-r--1--,.- ---1 ·1 · ·;--;--~- .. ---;-.-T- ·-;--:-·~r-~;-·- 2000 6 -2000 1000 . 6000 ::! -r-,---.,.--r--1--r--r- -100 ~t5o -250 PPM 17 9. 1.5 M Methanesulfonic acid in ethanol 0 at 20±1 ·c. I I I 'I I_ i Ii (ii I I j ii Ii Ii 1 I l' I I j I I I I I I I I I 11 I I I I I I I IJ I I I I I I I I I I I I I I I I I I I I 'I I I I I I I I JI I I I I I I I I ! I I I I I I I I I 11 I I I It I I I I' I I I I I I I I I I I I I I I I I 'JI I I I I I I I 'JI I I I (I I I I 210 .. ...... l.\J ...... 10. 1.5 M Methanesulfonic acid in ethanol - 33s at 20±1 ·c. \ I I I i~O a I I I 56 II I I I I • I L i I I J -101 ~too -. ') 11. 0.77 M Methanesulfonic acid in formamide - 170 at 20±1°C. I i : ~ §I -1-,-1-rrr-1--i-·;-·T-r-1·rr-1··r1-1-T-r·-i-1--i·-r.. 1-r-r~-i1-r-r-r-r--i~r-1-r1r-r-1-rl'1~-,-r-.,-1-ri"·11··r-rr; 1 1 , 1 r 12000 10000 8000 6000 4000 2000 0 HZ 12. 0.77 M Methanesulfonic acid in formamide - 33s at 20±1°C. nTfTnT]TITTPTIT[TffrfTTlTfTTITfflTT[TllT!111TjfTT11TTITfTIT1)11TI1TfT11TITTTTnTfn1T[TTITfTIIT[T1ITTflIT[T -40 -60 -80 -100 -120 -140 -160 -180 -200 -220 -240 HZ 17 13. 0.39 M Methanesulfonic acid in N-methylformamide - 0 at 20±1°C. -,--, b I I I I I I I I I I 78 0 7800 7750 I 76~0 I 7600 7500 ,, 0 ~ I I I 450 ~ 0 14. 1.5 M Methanesulfonic acid in N-methylformamide - 33s at 20±1°C. :-·--r--r-1-·-r-T- 1· -·r-·-~· -· l · - ,---·r---,- -r·- ;T-·. ···1--·r ;···1·-··1 ·-1-· -2000 ··400 -6000 HZ ..- -,-.--.-,----.- 1--r-1-1------r--,---,-,-1-..-...-.·1--1-.-•-r1--r--r 100 50 . 0 -50 -100 -250 PPM 15. 0.19 M Methanesulfonic acid in N,N-dimethylformamide - 170 at 20±1°C. I .• I 1 -·- _,__,_,__~-'--~----- 30000 20000 :odoo rj 0000 ·,~ $"lQ ... 0 s,... •• 1e~.o~ - o.«1' :!>1t..!173r1.-- ~ooth. I~ .. ~ N.. ~- ·r-r -r-r -, --t --r-r -1-·1--r --1--r-.-r-1--r-i----r-+- eobo 7500 1000 &sbo HZ -,--r-1--;-, --· r-r·r·-..--..--r--1-.--.--r 1--y--,--1-·--r-.---.--..--r-..--;r---.1--i--i--r-r-r•-r.--r1..--.~~,~--r-.~-~~~~~~~~- 600 ~00 200 . 0 -200 --~00 ?P~ 16. 0.19 M Methanesulfonic acid in N,N-dimethylformamide - 33s at 20±1"C. - ,_ -t---1---...... ,.-·-----·~·------2000 1000 ' · · ' · ·sdoo ·:,..:' · 1>'1·/,' t&.<;,(~So\.M.b~•I~ "" I' ·-----~-·---+--- I I I 1--i--r-,.-.--r.-r.--r'lr -..--r- -200 -250 " -300 ··3SO ·-.JOO HZ 17 17. 0.77 M Methanesulfonic acid in tetrahydrofuran - 0 at 20±1°C. 30000 20000 :oooo 6 :oooo ':.'. ~ .. ,o s. o Ii,,.., i\.'b'!>f"i•Ol"i' 11°1tJ'1' s..,~.•1~?>.~07· i•Ob't' 1'11·'!0!> I ., I ~ \ .....I T1+-rrr111TIT]Tnr! rrrr r n nT1-n 1'Tl1Tf1 Tl n r;rrrn rrn ~T:-;rr.·i r rn fJ n 1 ! , r1rr1 rr.1 I 7800 7600 7•100 7200 70bo 6800 6600 6400 H2 I ,, ,. SQ I ·•·.-~.· .. I el 'f ·~I --r-r-- ---r- --..--r--11--r --·r--·r-r--r-r1-~~r---r-~~-r--riTl-.-~..---.----T- 1 -r~.....--l....-~--..- ·-r--1--~- -T--r ·1··· T-r~-IT-T r-r --r 1 ' ' 600 . ' ' •lbO • ' 200 i ' ' . . ' d . . . ' . . -200. . . --400 ??M 18. 1.5 M Methanesulfonic acid in tetrahydrofuran - 33s at 20±1°C. -; -----1 ·-~- T--: ---:--· :- -; -·-:-·. ,-~~~~-,.---,--:---.--~-,- -.--,-,- ;;· -··-~~·~1~~~~:-- 1 .. ,--..-~~2000 .----:-.-.-,-- - .!000 6000 ,,~ .s,.,.,., L -o.11u-1o101 -..1.~oi..,, ..... t' :rn·q 'm: "~rm~n ~'' "" f'' •ccm\;, "'"'''·me:' n 'T"''l' nccn ~ ~_!~~~~~~~~j;·-~f~100 50 0 -SO ··100 -150 ··200 -250 PPM f-1 w 0 17 19. 1.5 M Methanesulfonic acid in dimethoxyethane - 0 at 20±1°C. 1···-·T -r-i- -,-·--·-r-··r- ·1-----r --r--·-r-,. ---,-----,--1-1·---i------r--r-.--1 r--1 ·-1 -; ----,- 1 l 0000 5000 d 5000 - !0000 · t5boo h~ Av·1t· ,~,.e~_Q). -<~e.e11"' S 11 ,.~ ~ o l:Z-5. ~ s, ... ,.-.:ie·""'" $,,~~ > ,,,. '7?>0 I I i I /\' ) 0 i ,!\._, \.i -· t ~ I _. ; ,V\_-" ! I .,---,--·-r•--.-r-r-11-r-r-T-rr--r·,-,-T,-.-.-r -.-...r--r ' ' ,- 5aoo .u.s.~ ..., ...... j J .._,.,....,.~...,,,~~ ~ f r-rrnTTTTTTTT1Tj"TTrrrrn·q-i-rnT'rrrrrmTT,TI J I I I I JrTTfTrTT"l"J'T I I J • I I I I I I I I J I I fTTrrl I J I I I I f1" I I I I I I I fTTTTTTTTI~ 700 sdo 500 400 300 2 0 ' iOO 0 -!00 -200 -300 PP!ol -400 I-' VJ I-' 20. 3.1 M Methanesulfonic acid in dimethoxyethane - 33s at 20±1°C. -, 2000 6000 ,,, -r---,---1- r-·-1 ·-- 1- --1··--r-1--1·---r---r---1---T-,----r---.--.---r-· -r T 100 50 0 -50 2SO PPM 17 21. 1.5 M Methanesulfonic acid in methyl carbitol - 0 at 20±1°C. 1111111111111111111111111111111111111111111111111111111111111111111,11111111 8000 7800 76 ~ 0 7 72 7 6 0 6 6~ ~ f) ~262 I I I I I I I 600 400 -200 -400 PPM 22. 0.77 M Methanesulfonic acid in acetone - 170 at 20±1°C. 5 0 400 3 0 200 100 -100 -200 PPM 23. 1.5 M Methanesulfonic acid in acetone - 33s at 20±1°C. ·""' I I I I I I I 1 1 1 2000 0 -2000 f -sdoo HZ \ 17 24. 3.1 M Methanesulfonic acid in dimethylsulfoxide - 0 at 20±1°C. )000 !0000 s., • • 0 $;1>10,0, f,.:tbo-1.207• 6·07~p,..._, S..,. • 1e>.05~-~.t.o1• i~\.!~7,,_, -1--.-,--,---,-T-r-r-.--r1-.--r 500 8000 . 7500 200 0 33 25. 0.39 M Methanesulfonic acid in dimethylsulfoxide - s at 20±1°C. I I 2000 0 -2000 I d(..,t.1,.)~~() .... 0 f .S"'~A .. -q,1'10-o.o• • -q.:z.;el'P,_ :r 11 ii 'I II ii :i: 16 11 ·I 0 Ii .,;"'0 11 I ,I I I I I I I I I I I I I I I I I I I I I I I I I I I I -150 -200 -250 -300 -350 100 50 17 26. 5.4 M Methanesulfonic acid in acetonitrile - 0 at 20±1°C. ~o~---- \-- --~- '~Y~~---~;;~-· r;~ --.-, --r-i-:-;-~-:---r-, T--:--r--r-; -.--,- 0 -200 1 ~(1: .,.,;~ ""' .. r g I ~ j i •. , ..•. , .•••1, ...• , .••• ~00 7600 7400 7200 7000 6800,~ 6600 6400 6200 HZ 600 -400 PPM I-' w 00 't ·1 TIS at 20±1°C. 27. 3. 9 M Methanesulfonic acid in acetoni ri e - 6000 ' I . '" 10n 50 0 -50 -100 -150 -200 17 28. 0.41 M Trifluoromethanesulfonic acid in water - 0 at 20±1°C. I -10000 HZ ,, ~ ?; ~ ;1 ",i :1 'I Ii !i 11 II I! I , I . \ M I f1 \r-·M II ...... ______6.. 5... • .....o ... , __... 6... 4.. 0...... 0... 0 __ ...... ,i ...... , .._...'<,...... '""""' •14'••1 .. •11+1;140--~,;.63 1._''*""'4•4i '·"-·"""~ "' ",.,.,.,~~"""",~... ~ ....., _____W'lo" ____•._,...._., __ ,,,., .. , ___ _ L')\II, L t ._,., 44 • ., 'lt,Pli I 1 • .. ... 600 400 200 0 -200 -400 PPM 33 29. 4.9 M Trifluoromethanesulfonic acid in water - 8 at 20±1°C. r - -- -. ------2000 ------=r6000 808( :-:------i--r- --T-·---r---i----;--~ 50 Ii 17 30. 0.21 M Trifluoromethanesulfonic acid in water - 0 at 50±1°C. 0000 20000 '.0000 . '.0000 . ·: I 4"11·J,.."'"t~."4-'i'li't. lqO ~ ,1')0 .... --.. i .. : ·- T 33 31. 8.8 M Trifluoromethanesulfonic acid in water - s at 50±1°C. 2000 0 2000 ---, -250 -300 ?P 32. 1.1 M Methanesulfonic acid sodium salt with stoichiometric amounts of 18-crown-6 17 in water - 0 at 20±1°C. I I I I I I I I I I I I I I I II I I I II I I I II I ii I I I Ii I I I ii I I I I I I I I I I I lj I I I I I I I I I I I I I I I I I II [ I I 7400 7300 7200 7100 7000 6900 6800 HZ I I I I I I I I I I I I I I I I BOO 600 400 200 -200 PPM 33. 1.6 M Methanesulfonic acid sodium salt with stoichiometric amounts of 18-crown-6 in water - TIS at 20±l"C. l ~ D ~ II I \ . I ! I II ' I i t;.. .; I I I I I J I I I I I I I I I b I I I l I I I I I b I I I I I I I I I I - 0 -100 -1 0 -200 -2 0 -300 HZ -350 I I I I I ··~--,~~-~~~~~-r' 100 50 d I -1b0 -50 -100 -200 -250 PPM -300 146 APPROVAL SHEET The dissertation submitted by Telitha Marie Murray has been read and approved by the following committee: Dr. David Crumrine, Director Associate Professor, Chemistry, Loyola Dr. Elliott Burrell Associate Professor, Chemistry, Loyola Dr. A. Keith Jameson Professor, Chemistry, Loyola Dr. Daniel Graham Assistant Professor, Chemistry, Loyola Dr. David Lankin Senior Scientist, G. D. Searle Company The final copies have been examined by the director of the dissertation and the signature which appears below verifies the fact that any necessary changes have been incorporated and that the dissertation is now given final approval by the Committee with reference to content and form. The dissertation is therefore accepted in partial fulfillment of the requirements of the degree of Doctor of Philosophy. J~ J99L-· i Date ~ Director's Signature