AN ABSTRACT OF THE THESIS OF PETER BERNARD DEGROOTfor the DOCTOR OF PHILOSOPI-Tv (Name) (Degree) in CHEMISTRY presented on 2A_)7` /967 (Major) (Date) Title: RADIOSULFUR EXCHANGE STUDIES IN THE LIQUID SULFUR DIOXIDETHIONYL FLUORIDE SYSTEM Abstract approved: Redacted for Privacy T.I H. Norris A system of gas chromatographic separation of the components of the radio-exchange system thionyl fluoride--sulfur dioxide and subsequent radioassay of these species in a flow-through ionization chamber has been developed. The column used, a 1 m x 4 mm Pyrex helix packed with 40/60 mesh Chromosorb T (Teflon) with a 20% by weight Haloca.rbon 10-25 oil liquid phase coating, gave re- tention times (to peak maxima) of approximately 40 and 100 seconds for thionyl fluoride and sulfur dioxide, respectively, with a helium carrier gas flow rate of 35.3 ml /rain at a column temperature of 40.00C.Specific activities of the exchanging components, obtained from the electronically integrated gas chromatograph peak area and the activity as measured by a vibrating-reed electrometer in con- junction with the ionization chamber, were found to be reproducible to approximately ± 10%. The above technique was applied to several investigations of 35Sexchange between liquid thionyl fluoride and liquid sulfur dioxide: (1) Uncatalysed exchange.Uncatalysed exchange between thionyl fluoride and sulfur dioxide was investigated at 25. 0oC and mole ratios of SOF2: SOof approximately 6:1, 1:1, and 1: 6.No 2 evidence of any exchange was found for periods of as long as 150 days, despite evidence of chemical reaction having occurred in some of the long term samples. (2) Lithium fluoride (Lewis base) catalysis. No exchange was observed up to 123 days in the heterogeneous system lithium fluoride--thionyl fluoridesulfur dioxide at ambient temperature and approximately 1: 1 mole ratios of SOF2; SO2. There was again evidence of chemical reaction having taken place in the system. (3) Antimony(V) fluoride (Lewis acid) catalysis. Antimony(V) fluoride was found to exert a moderate catalytic action, with the apparent order in catalyst ranging from about 0.5 in excess thionyl 35S fluoride to about 0.9 in excess sulfur dioxide.The exchange in this homogeneous system was investigated throughout the concen- tration range from approximately 6: 1 to 1: 6 mole ratios of SOF2: SOat temperatures of 0.0, 25.0, and 40. 0oC. The results 2 were found to fit a rate law of the form Rate = k(SOF2) [z] K [ (S02) - z] 2[ (SbF5)2] where square brackets denote equilibrium concentrations, and [ z] is the concentration of the adduct S02SbFformed from a reaction 5 of sulfur dioxide with the dimeric species (SbF5)2, postulated as being the predominant form in which antimony(V) fluoride exists in solutions containing excess thionyl fluoride.The following mech- anism has been proposed: 2 S*0+ (SbF5)2 = 2S*02SbF(fast) 2 5 SOF+ S SbF= S OF 2. SbF+ SO2 (slow) 2 z 5 5 Values found for the rate constant,k,at 0, 25, and 40°C are, 2 1hr1. respectively, 2.2 X103,1.6 X 10-2,and 9.1 X 10M The equilibrium constant, K ,was found to be about 3 X10-3M-1at 25oC, and of the order of 10-3 at 40oC. The Arrhenius activation energy was found to be about 15 kcal/mole, and the entropy of acti- vation was found to be approximately -55 cal/mole-°K. The rather low degree of catalysis by antimony(V) fluoride, the large negative entropy of activation, and the variable and non- integral apparent order in catalyst as well as the absence of exchange in the uncatalysed experiments are interpreted as indications that molecular mechanisms involving Lewis acid-base interactions are of primary importance in these systems, in contrast to the solvent self-ionization required by the "solvent systems" picture of non- aqueous reaction mechanisms. Radiosulfur Exchange Studies in the Liquid Sulfur DioxideThionyl Fluoride System by Peter Bernard De Groot A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy June 1970 APPROVED: Redacted for Privacy Professor of Chemistry in charge of major Redacted for Privacy Chairman of Department of Chemistry Redacted for Privacy Dean of Graduate School Date thesis is presented November 14, 1969 Typed by Donna L. Olson forPeter Bernard De Groot ACKNOWLEDGEMENT I wish to thank Dr. T. H. Norris for his guidance and patience during the course of these studies. I also wish to thank Mr. Mike Gilbert for his assis- tance with the computer programs and procedures. This investigation was sponsored in part by the United States Atomic Energy Commission under contract AT(45-1)-244 between the commission and Oregon State University. TABLE OF CONTENTS Chapter Page I.INTRODUCTION 1 II.EXPERIMENTAL A.General B.Preparation and Purification of Materials 10 1.Antimony(V) Fluoride 10 2.Thionyl Fluoride 12 3.Sulfur Dioxide 14 4.Labeled Sulfur Dioxide 14 5.1,2 - Dichloroethane 18 C.Analytical Methods 18 1.Sulfur 18 2.Antimony 19 D.The Separation and Radioassay System 27 1.General Considerations 27 2.The Completed System 29 3.The Gas Chromatograph 32 a.Column Selection and Preparation 32 b.Sample Injection 36 c.Column Temperature Control 40 d.Detector Temperature Control 40 e.Carrier Gas Flow Rate 42 f.Thermistor Bridge Potential 42 4.The Integrator 42 5.The Ionization Chamber--Electrometer 48 a.Sensitivity 48 b.Ionization Chamber Potential 48 c.Counting Gas Flow Rate 49 6.Calibration of the Separation and Radioassay System 49 a.The Gas Chromatograph 50 b.The Ionization Chamber--Electrometer 50 c. Summary of Calibration Results 53 E.Run Procedures 55 1.Dosing 55 a. Antimony(V) Fluoride 57 b.Thionyl Fluoride 60 c.Sulfur Dioxide 62 2.Separation and Radioassay 62 3.Antimony Analysis 67 F.Data 68 Chapter Page III. METHODS OF CALCULATION 87 A.Specific Activity 87 B.Concentration 88 C.Fraction Exchange and Rate of Exchange 89 D.Rate Dependence on Concentrations 90 E.Linear Least Squares Analyses 91 F.Rate Law Model Calculations 92 1.Non-Linear Least Squares Analysis 92 2.Estimation of Rate Law Parameters 98 3.Theoretical Order in Catalyst 100 G. Activation Parameters 101 IV. RESULTS AND DISCUSSION 102 A. Identification of Initial Gas Chromatograph Peak 102 B.Evidence for Complex Formation 104 C.Uncatalysed Experiments 106 D.Lithium Fluoride Catalysed Experiments 107 E. Antimony(V) Fluoride Catalysed Experiments 109 1.Results 109 2.Concentration Dependences of the Exchange Rate 117 a.Order in SbF5 117 121 b. Order in SOF2and SO2 3.Estimation bf Rate Precision 122 4.The Rate Law 127 5.Activation Parameters 137 6.Exchange Mechanism and Discussion 140 F. Separation and Radioassay System Performance 146 V. SUMMARY 151 BIBLIOGRAPHY 154 APPENDIX 159 LIST OF FIGURES Figure Page 1. Density of SOFvs. Temperature. 16 2 2. Transmittance vs. Wavelength for a Solution of SbFin 1, 2- Dichloroethane. 22 5 3. Absorbance at 463 Millimicrons vs. Concentra- tion of SbFin 1,2-Dichloroethane. 25 5 4. Block Diagram of the Separation and Radio - assay System. 30 5. Vapor Sample Injection System for the Gas Chromatograph. 38 6. Chopper Stabilized Integrator. 44 7. The Dosing Section of the Vacuum Line. 56 8a. Oil and Mercury Manometer System. 58 8b. SbFLiquid Storage Bulb. 58 5 9. Sample Bomb Breaker. 64 10. Strip Chart Records for Experiment K15-2, Sample b. 66 11. McKay Plot for Experiment Group K9, Corrected to Unit SbFConcentration. 116 5 12. Exchange Rate Dependence on SbF5 Concentration at Approximately 6: 1 Mole Ratio of SOF2: 502 and 25.0°C. 118 13. Exchange Rate Dependence on SbF5 Concentration at Approximately 1: 1 Mole Ratio of SOF2: SO2 and 25.0°C. 119 14. Exchange Rate Dependence on SbF5 Concentration at Approximately 1: 6 Mole Ratio of SOF2: SO2 and 25.0°C. 120 Figure Page 15. Approximate Exchange Rate Dependence on SOFConcentration in Excess SO2 at 25 °C. 123 2 16. Approximate Exchange Rate Dependence on SO2 Concentration in Excess SOF2at 25 C. 124 17. Graphical. Estimation of Rate and Equilibrium Constants. 131 18. Rate Constant,k,vs. SO2 Concentration for o 25.0C Data with Ke =3.59"X 103. 134 19. Temperature Dependence of the Exchange Rate Constant,k. 139 20a. Possible Transition State for the Exchange. 143 20b. Possible Transition State for the Exchange. 143 LIST OF TABLES Table Page 1. Vapor Pressure of Thionyl Fluoride. 12 2. Density of Thionyl Fluoride at Various Temperatures. 15 3. Standardization of Absorbance at 463 mp. of Solutions of SbF5 in 1,2-Dichloroethane. 24 4. Absorbance of SbFSolutions in 1, 2- Dichloroethane Containing Halocarbon5 Stopcock Grease, SOF2, and SO2. 26 5. Columns Tested for Gas Chromatographic Separations. 33 6. Calibration of the Chromatograph with SOF2. 51 7. Calibration of the Chromatograph with SO2. 52 8. Calibration of the Ionization Chamber--Electrometer. 54 9. Uncatalysed Exchange of Sulfur-35 Between SOF2 and SO2 at 25.0 C. 69 35S 10. SbF5 Catalysed Exchange of Between SOFand 2 SO2 at 0.0°C. 71 35S 11. SbFCatalysed Exchange of Between SOFand 5 o 2 SO2 at 25.0C. 73 12. SbFCatalysed Exchange of35S 5 Between SOF2and SO2 at 40. 0 °C. 83 13. Test for Heterogeneous Catalysis by Lithium Fluoride at Ambient Temperature. 86 14. Rates of SbF 5Catalysed Sulfur-35 Exchange Be- tween SO2 and SOF2. 111 15. CorrectedValues of (1-F) for Group K9. 114 Table Page 16. Observed and Expected Sulfur Dioxide Specific Activities in Several Representative Experiments. 117 17. Rate Constants for Experiments at 25. 0 °C. 133 RADIOSULFUR EXCHANGE STUDIES IN THE LIQUID SULFUR DIOXIDETHIONYL FLUORIDE SYSTEM I.INTRODUCTION Over the past two decades, isotopic exchange and other experi- ments, primarily in sulfur-containing non-aqueous solvents, have been conducted in this laboratory.1 Results of these experiments as well as work by others have generally been interpreted in terms of Lewis acid-base concepts and molecular processes, in contrast to the "solvent system" theory advanced by Cady and Elvy (1928) and developed extensively by G.