Computational and Experimental Evidence on Reaction Mechanisms of Oxidized Sulfur-Containing Compounds in Ground and Excited States Jerry W

Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 2001 Computational and experimental evidence on reaction mechanisms of oxidized sulfur-containing compounds in ground and excited states Jerry W. Cubbage Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Organic Chemistry Commons, and the Physical Chemistry Commons Recommended Citation Cubbage, Jerry W., "Computational and experimental evidence on reaction mechanisms of oxidized sulfur-containing compounds in ground and excited states " (2001). Retrospective Theses and Dissertations. 419. https://lib.dr.iastate.edu/rtd/419 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. 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Jenks Iowa State University Ames, Iowa 2001 UMI Number: 3003233 ® UMI UMI Microform 3003233 Copyright 2001 by Bell & Howell Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. Bell & Howell Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 ii Graduate College Iowa State University This is to certify that the Doctoral dissertation of Jerry W. Cubbage has met the dissertation requirements of Iowa State University Signature was redacted for privacy. Signature was redacted for privacy. Signature was redacted for privacy. For th^Gfaduate College iii To Julia My best friend! iv TABLE OF CONTENTS GENERAL INTRODUCTION 1 Dissertation Organization 1 Objectives 2 Nomenclature 2 CHAPTER 1: THERMOLYSIS OF ALKYL SULFOXIDES AND DERIVATIVES: A COMPARISON OF EXPERIMENT AND THEORY 4 Introduction 4 Results 33 Discussion 62 Conclusions 73 Experimental Section 73 References 82 CHAPTER 2: Ei ELIMINATION: ANUNPRECEOENTED FACET OF SULFONE CHEMISTRY 89 Abstract 89 Introduction 89 Results 93 Discussion 97 Conclusions 99 Experimental Section 100 References 104 CHAPTER 3: COMPUTATIONAL STUDIES OF THE GROUND AND EXCITED STATE POTENTIAL OF DMSO AND H2SO: RELEVANCE TO PHOTOSTEREOMUTATION 107 Introduction 107 Computational Methods 118 Results 119 Discussion 140 V Conclusions 142 References 142 CHAPTER 4: BIMOLECULAR PHOTOREDUCTION OF AROMATIC SULFOXIDES 146 Introduction 146 Results 149 Discussion 169 Conclusions 175 Experimental Section 175 References 178 GENERAL CONCLUSIONS 180 APPENDIX 1 : KINETIC PLOTS FOR SULFOXIDES AND DERIVATIVES 182 APPENDIX 2: GEOMETRIES OF SULFOXIDES, SULFINYL DERIVATIVES, AND TRANSITION STATES 185 APPENDIX 3: GEOMETRIES OF SULFENIC ACIDS 201 APPENDIX 4: GEOMETRIES OF OLEFINS 203 APPENDIX 5: ACTIVATION ENTHALPIES FOR ALL SULFOXIDES AND DERIVATIVES 208 APPENDIX 6: HEATS OF REACTION FOR ALL SULFOXIDES AND DERIVATIVES 212 APPENDIX 7: INTRINSIC REACTION COORDINATES 216 APPENDIX 8: COORDINATES FOR SULFOXIDES AND DERIVATIVES IN CHAPTER 1 221 APPENDIX 9: DATA FOR SULFONES IN CHAPTER 2 330 APPENDIX 10: COORDINATES FOR SULFOXIDES IN CHAPTER 3 336 ACKNOWLEDGMENTS 345 1 GENERAL INTRODUCTION Dissertation Organization This dissertation is organized into four chapters. Chapter 1 focuses on the thermal elimination of sulfoxides and sulfinyl derivatives and the comparison of computational and experimental studies. Chapter 2 presents the thermolysis of analogous sulfones and classification of this elimination reaction mechanism. To gain insight on the photostereomutation mechanism, a comprehensive computational study of the excited state potentials for H2SO and DMSO is covered in Chapter 3. The emphasis of Chapter 4 is on the photo-assisted reduction of sulfoxides. Chapters 1, 3, and 4 will be the basis for future publications. Chapter 2 is based on a published paper. Within Chapter 1, there is a brief review of where this reaction has been used in the synthetic community. There is also a comprehensive introduction to the class of elimination mechanism (Ei reaction) for analogous molecules and sulfoxides. This includes both experimental and computational facts presented in the previous literature on Ei reactions. The results and discussion will present both computational and experimental activation barriers that compare closely for the sulfoxide elimination. While the author completed the great majority of this work, Dr. Yushen Guo initiated the first experimental studies for Chapter 1. Chapter 2 is an extension of the Ei reaction extensively evaluated in Chapter 1 to sulfone chemistry. A brief introduction discusses the previously known thermal reaction of sulfones. Both computational and experimental results present data that allow classification of this reaction as an Ei reaction. Brian Vos prepared one of the deuterated starting compounds in preparation of the sulfone used in the isotope study. Switching gears to photochemistry in Chapter 3, the introduction is fairly comprehensive covering both thermal-chemical and photochemical events relevant to stereomutation of sulfoxides. The results present a relatively complicated computational study for HaSO and DMSO. The discussion focuses on the elucidation of mechanism of photostereomutation. Dr. William Jenks produced some of the optimized geometries used in the study. 2 In Chapter 4, there is a brief introduction into the chemical reduction of sulfoxides as well as a limited discussion of past photochemical studies. The bulk of this chapter is devoted to results and discussion of various experiments examining the photo-assisted reduction of certain alkyl aryl and diaryl sulfoxides. Troy Tetzlaff and Heather Groundwater in part carried out the work in this chapter. Objectives This dissertation contains an overall theme of deducing reaction mechanisms of sulfur and oxygen containing compounds. The processes in the first two chapters are related by using gas- phase kinetics, isotope effects, and computational chemistry to better understand the mechanism that is operating for the thermolysis of sulfoxides, sulfinyl derivatives, and sulfones. The third chapter is a computation project designed to aid in understanding the details of the mechanism of photostereomutation of sulfoxides. The fourth chapter describes the deduction of the mechanism operating in sulfoxide reduction photochemistry. All in all, this dissertation should provide evidence of the different processes that work either by thermal or photochemical means for sulfur and oxygen containing compounds. Another underlying theme presented in this dissertation is the relevance and usefulness of computational quantum chemistry to real orgainc systems. It is utilized throughout the first three chapters to aid in the deduction of reaction mechanisms. In the first two chapters, it provided information in the form of transition state geometries, which were previously unknown. It also provided added information on the elimination reaction energetics of molecules that could not be characterized by experiment. In Chapter Three, computational chemistry allowed access to the excited state potential energetics. Excited state geometries, which were previously unknown, are obtained from quantum chemical calculations. The use of computational chemistry also provided information for future experiments. Finally, it is shown in this dissertation the pivotal role computational chemistry can play in deducing reaction mechanisms. Nomenclature Lastly, because of the multitude of sulfur oxidation states, and the relative unfamiliarity of many chemist with their nomenclature, Figure 1 is intended as a quick reference guide. Throughout 3 this manuscript, sulfoxides have been written in the octet obeying ylide form (see

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