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Substituent Effects in Acid-Catalyzed Hydration of Alkenes

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Substituent Effects in Acid-Catalyzed Hydration of Alkenes UNIVERSITY OF OKLAHOMA GRADUATE COLLEGE MECHANISTIC INVESTIGATION OF ADDITIONS TO ALKENES BY USING CORRELATIONS A DISSERTATION SUBMITTED TO THE GRADUATE FACULTY in partial fulfillment of the requirements for the Degree of DOCTOR OF PHILOSOPHY By RUIBO LI Norman, Oklahoma 2009 MECHANISTIC INVESTIGATION OF ADDITIONS TO ALKENES BY USING CORRELATIONS A DISSERTATION APPROVED FOR THE DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY BY Donna J. Nelson Marilyn Breen Chuanbin Mao Robert P. Houser Michael T. Ashby © Copyright by RUIBO LI 2009 All rights reserved. Acknowledgements I would first like to give my great appreciation to my advisor, Dr. Donna Nelson, for offering me the opportunity to work and study in her research group. I am truly grateful for her guidance, patience, encouragement, and financial support. Without her direction and support, it would not be possible for me to complete this research project. I would also like to thank the other members of my Graduate Advisory Committee, Dr. Marilyn Breen, Dr. Chuanbin Mao, Dr. Robert Houser, Dr. Michael Ashby, and previous member Dr. Rudi Wehmschulte. Their feedback and advice are always helpful for me throughout my graduate studies. Next I would like to thank all my group members, Christopher Brammer, Heather Rhoads, Dr. Jaisankar, and Dr. Perumal for their friendship and support. I would also like to give special thanks to my project collaborator Christopher Brammer for his work in calculating most of the alkene HOMO/LUMO energies and in solving computer problems. For financial support of our researches, I would like to thank the National Science Foundation, Lucent Technologies, McEvoy Financial Corp., the John Simone Guggenheim Foundation, Sloan Foundation, the Oklahoma Center for Advancement of Science and Technology, the Ford Foundation, and the Robberson Research Grant. Last but not least, I would like to thank my dear wife Hanlie and son Saifu for their support, encouragement, and love. iv Table of Contents Acknowledgements iv Table of Contents v List of Tables viii List of Figures ix List of Equations xi List of Schemes xiii List of Abbreviations xiv Abstract xv Chapter 1 Introduction 1 1.1 The objective of the project 1 1.2 Chemical reactivity 2 1.3 LFERs method 4 1.3.1 Hammett equation 4 1.3.2 Extensions of Hammett equation 5 1.3.3 Separation of polar and steric effects 7 1.3.4 Dual-parameter substituent constants 9 1.3.5 Approximate nature of LFERs 10 1.4 Steric effect measurements 12 1.5 Research methodology 12 1.6 Linear regression 18 1.7 Significance of the project 20 1.8 Development of the methodology 22 1.9 References 24 Chapter 2 Substituent Effects in Acid-Catalyzed Hydration of Alkenes 31 2.1 Introduction 32 2.2 Competitive reaction experiments 33 2.2.1 Materials 33 2.2.2 Instruments 33 2.2.3 Experiment procedure 34 2.3 Correlation plots 37 2.4 Substituent effects 41 2.5 Comparison with a previous study 43 2.6 Comparison among similar electrophilic additions to alkenes 48 2.7 Conclusion 52 2.8 References 52 Chapter 3 Mechanistic Investigation on Alkene Reactions with Several Transition Metal Compounds via Correlations 58 3.1 Correlations in alkene oxidations with chromyl chloride (CrO2Cl2) and with chromic acid (H2CrO4) 59 3.1.1 Introduction 59 3.1.2 Oxidation with CrO2Cl2 61 v 3.1.3 Oxidation with H2CrO4 64 3.1.4 Correlation plots 65 3.1.5 Electronic effects versus steric effects 71 3.1.6 Differentiating between the proposed mechanisms 74 3.1.7 Conclusion 85 3.2 Correlations in oxidation of alkenes with palladium chloride (PdCl2/H2O), the Wacker oxidation 85 3.2.1 Introduction 85 3.2.2 Correlation plots 91 3.2.3 Substituent effects 95 3.2.4 Mechanistic analysis 96 3.2.5 Conclusion 106 3.3 Correlations in homogeneous hydrogenation of alkenes in the presence of Wilkinson's catalyst, RhCl(PPh3)3 107 3.3.1 Introduction 107 3.3.2 Proposed mechanisms 108 3.3.3 Correlation plots 112 3.3.4 Substituent effects and mechanistic analysis 118 3.3.5 Comparison with Wacker Reaction 119 3.3.6 Conclusion 123 3.4 References 123 Chapter 4 Substituent Effects in Alkene Halogenations 137 4.1 Substituent effects on alkene reactivities in bromination and in chlorination of alkenes 138 4.1.1 Introduction 138 4.1.2 Correlation plots 139 4.1.3 Alkene bromination 143 4.1.4 Alkene chlorination 145 4.1.5 Comparing chlorination with bromination 146 4.1.6 Conclusion 147 4.2 Substituent effects in alkene complexation with iodine 148 4.2.1 Introduction 148 4.2.2 Correlation plots 148 4.2.3 Substituent effects 152 4.2.4 Conclusion 154 4.3 Substituent effects in additions of ISCN and ICl to alkenes 154 4.3.1 Introduction 154 4.3.2 Correlation plots 156 4.3.3 Electronic effects versus steric effects 159 4.3.4 Patterns in the plot 160 4.3.5 Comparison with other alkene halogenations 162 4.3.6 Conclusion 166 4.4 References 166 Chapter 5 Computational Methods 172 vi 5.1 Introduction 173 5.2 MNDO method 175 5.3 Ab initio methods 176 5.4 Evaluation of the MO computational methods 178 5.5 Substituent effects on alkene IPs (or HOMO energies) 185 5.6 Substituent effects on alkene EAs (or LUMO energies) 187 5.7 Conclusion 188 5.8 References 188 Chapter 6 Conclusion 192 6.1 Summary of the project 192 6.2 Directions for future studies 196 Appendix: Copies of reprints of five published papers that correspond to the studies included in Chapters 3 and 4 196 vii List of Tables Table 2-1 Relative rates from the competitive reaction experiments in H2SO4 (60%) at 50°C 37 Table 2-2 Alkene IPs (eV), HOMO energies (eV), and relative rates of acid-catalyzed hydration of alkenes in aqueous H2SO4 (60%) at 50°C 39 Table 2-3 Alkene IPs (eV), HOMO energies (eV), and relative rates of acid-catalyzed hydration of alkenes from Tidwell’s study 44 Table 3-1 Alkene IPs (eV), HOMO energies (eV), and relative rates of chromyl chloride (CrO2Cl2) oxidation of alkenes 66 Table 3-2 Alkene IPs (eV), HOMO energies (eV), and relative rates of chromic acid (H2CrO4) oxidation of alkenes 67 Table 3-3 Relative reactivities of alkenes in three reactions 80 Table 3-4 Alkene IPs (eV), HOMO energies (eV), LUMO energies (eV), and relative rates of palladium chloride oxidation of alkenes 92 Table 3-5 Alkene IPs, LUMO energy levels, and relative rates of catalytic hydrogenation of alkenes by using Wilkinson's catalyst (A) 112 Table 3-6 Alkene IPs, LUMO energy levels, and relative rates of catalytic hydrogenation of alkenes by using Wilkinson's catalyst (B) 113 Table 4-1 Alkene IPs (eV), HOMO energies (eV), and relative reaction rates of bromination and chlorination of alkenes 139 Table 4-2 Alkene IPs (eV), HOMO energies (eV), and relative equilibrium constants of alkene complexation with solid iodine 149 Table 4-3 Alkene IPs (eV), HOMO energies (eV), and relative rates of additions of ISCN and ICl to alkenes 157 Table 5-1 Alkene IPs, EAs, HOMO energies, and LUMO energies (eV) 180 Table 5-2 Correlation coefficients of alkene IPs versus HOMO energies and EAs versus LUMO energies for five different MO methods 185 viii List of Figures Figure 1-1 Schematic diagram showing the relationship between the two parameters (ΔG‡ and ΔG°) and the free energies of reactants (R), products (P), and transition state (TS) 3 Figure 1-2 Plots of log krel values (a) versus alkene IPs and (b) versus alkene HOMO energy levels for alkene bromination, an electrophilic addition to alkenes without strong steric effects 15 Figure 1-3 Plots of log krel values (a) versus alkene IPs and (b) versus alkene HOMO energy levels for alkene hydroborotion, an electrophilic addition to alkenes with strong steric effects 16 Figure 1-4 Schematic diagrams showing the plots of log krel values versus alkene LUMO energy levels for a nucleophilic addition to alkenes (a) without strong steric effects or (b) with strong steric effects 17 Figure 2-1 The GC chromatograms for competitive hydration of 2,3-dimethyl -2-butene versus 1-hexene: (a) initial reactants and (b) final reaction products 35 Figure 2-2 The plot of the log krel values for acid-catalyzed hydration of alkenes versus alkene IPs 40 Figure 2-3 The plot of the log krel values for acid-catalyzed hydration of alkenes in Tidwell’s study versus alkene IPs 45 Figure 2-4 Asymmetric transition state structures in the rate-determining steps in (a) hydroboration, (b) oxymercuration, and (c) acid- catalyzed hydration 49 Figure 2-5 Sterically equivalent transition state structures in diimide Reduction 50 Figure 2-6 Sterically equivalent pairs of complexes in (a) iodine complexation and (b) silver ion complexation 50 Figure 3-1 The plot of the log krel values vs. correspondent alkene IPs for alkene oxidation with CrO2Cl2 68 Figure 3-2 The plot of the log krel values for chromyl chloride oxidation of alkenes versus correspondent alkene HOMO energies 69 Figure 3-3 The plot of the log krel values for chromic acid oxidation of alkenes versus correspondent alkene IPs 70 Figure 3-4 The plot of the log krel values for chromic acid oxidation of alkenes versus correspondent alkene HOMO energies 71 Figure 3-5 Plot of log Krel values versus alkene IPs for alkene complexation with silver ion 78 Figure 3-6 Plot of log Krel values versus alkene IPs for complexation with molecular iodine 79 Figure 3-7 Plot of log krel values versus alkene alkene IPs for Wacker oxidation 93 Figure 3-8 Plot of log krel values versus alkene HOMO energies for Wacker oxidation 94 ix Figure 3-9 Plot of log krel values versus alkene LUMO energies for Wacker oxidation 95 Figure 3-10 The plot of the log krel values for homogeneous hydrogenation of alkenes by using Wilkinson’s catalyst
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