UNIVERSITY of CALIFORNIA, SAN DIEGO Insights Into Chemical
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UNIVERSITY OF CALIFORNIA, SAN DIEGO Insights into Chemical Reactivity: I. Computational Study of the Primary Versus Secondary O-18 Equilibrium Isotope Effects on Acidity, II. Low-temperature Studies on the Hydrogen-bond Symmetry of Hydrogen Cyclohexene-1,2-dicarboxylate Monoanion in an Organic Medium, III. Computational Study of the Base-catalyzed Decomposition of Malonic Anhydride A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Chemistry by Kathryn D. Burke Committee in charge: Professor Charles L. Perrin, Chair Professor Joshua S. Figueroa Professor Nathan C. Gianneschi Professor Joseph M. O’Connor Professor Melvin Y. Okamura 2013 Copyright Kathryn D. Burke, 2013 All rights reserved. The dissertation of Kathryn D. Burke is approved, and it is acceptable in quality and form for publication on microfilm and electronically: Chair University of California, San Diego 2013 iii DEDICATION To Travis Fork, Knife, Spoon iv TABLE OF CONTENTS Signature Page ............................................................................................................... iii Dedication ...................................................................................................................... iv Table of Contents ........................................................................................................... v List of Figures ................................................................................................................. x List of Tables ............................................................................................................. xviii Acknowledgements ................................................................................................. xxxvi Vita ........................................................................................................................ xxxviii Abstract of the Dissertation ..................................................................................... xxxix Chapter 1. Computational Study of the Primary Versus Secondary O-18 Equilibrium Isotope Effects on Acidity .................................................................. 1 Introduction ........................................................................................................ 1 The Effect of Isotopes on Vibrational Frequencies ................................ 3 Calculation of Equilibrium Isotope Effects ............................................ 5 Techniques for Experimentally Measuring EIEs on Acidity ................. 7 Secondary EIEs on Acidity of 18O-Labeled Acids ................................. 9 Effect of Isotopic Labeling of Acid Proton on Secondary 18O EIEs on Acidity ............................................................................. 12 Research Goals ................................................................................................. 13 Experimental ..................................................................................................... 16 Computational Methods ....................................................................... 16 Treatment of Isotopomers and Isomers ................................................ 19 v Brønsted Acids Centered on Carbon .................................................... 22 Brønsted Acids Centered on Nitrogen .................................................. 26 Brønsted Acids Centered on Boron ...................................................... 27 Brønsted Acids centered on Phosphorus .............................................. 30 Lewis Acids Centered on Carbon ......................................................... 36 Lewis Acids Centered on Nitrogen ...................................................... 37 Lewis Acids Centered on Boron ........................................................... 39 Lewis Acids Centered on Phosphorus .................................................. 43 Results .............................................................................................................. 44 Computational Results for Hydroxide .................................................. 45 Computational Results for Formic Acid, Protonated Formic Acid, and Formate ......................................................................... 46 Computational Results for Acetic Acid and Acetate ............................ 57 Computational Results for Carbonic Acid, Bicarbonate, Carbonate, and Carbon Dioxide .................................................... 59 Computational Results for Nitrogen-Centered Acids with Respective Conjugate Bases ......................................................... 66 Computational Results for Boron-centered Acids with Respective Conjugate Bases ......................................................... 74 Computational Results for Phosphorus-centered Acids with Respective Conjugate Bases ......................................................... 87 ZPE Differences ................................................................................... 98 vi Calculated 18O EIEs on the Acidities of Formic Acid and Derivatives .................................................................................. 101 Calculated Primary and Secondary 18O EIEs on the acidities of C, N, B, and P-Containing Brønsted Acids................................. 103 Calculated Primary and Secondary 18O EIEs on the acidities of C, B, and P-Containing Lewis Acids .......................................... 106 Discussion ....................................................................................................... 108 Reliability of EIE Calculations ........................................................... 108 Solvation Effects ................................................................................ 111 Errors in the Calculations ................................................................... 114 Comparing the Magnitude of Primary and Secondary EIEs— Vibrational Frequencies and the MMI Factor ............................. 115 Isotopic Substitutions of Formic Acid ................................................ 119 Magnitude of Brønsted Acid EIEs ..................................................... 120 Magnitude of Lewis Acid EIEs .......................................................... 126 Conclusions .................................................................................................... 128 Works Cited .................................................................................................... 131 Chapter 2. Low-temperature Studies on the Hydrogen-bond Symmetry of Hydrogen Cyclohexene-1,2-dicarboxylate Monoanion in an Organic Medium ............................................................................................................... 134 Introduction .................................................................................................... 134 Hydrogen Bond Symmetry ................................................................. 135 vii Are Symmetric Hydrogen Bonds Unusually Strong? ........................ 137 Other Donors in Hydrogen Bond Systems ......................................... 138 NMR Isotopic Perturbation and Isotope Effects on NMR Spectra .... 139 Previous Results and an Alternative Interpretation ............................ 146 Research Proposal .............................................................................. 148 Experimental ................................................................................................... 149 Materials ............................................................................................. 149 Instrumentation ................................................................................... 150 18 Synthesis of 1- O0–4 ........................................................................... 151 NMR Sample Preparation and NMR Spectra ..................................... 153 Results ............................................................................................................ 155 18O Isotopologues of 2 ........................................................................ 155 13 18 CH2 C NMR Signals for O Isotopologues of 1 ............................. 155 Carboxyl 13C NMR Chemical Shift Assignments for 18O Isotopologues of 1 ....................................................................... 155 Carboxyl Carbon Temperature Studies .............................................. 161 Ipso Carbon Chemical Shift Assignments .......................................... 163 Ipso Carbon Temperature Studies ...................................................... 166 Discussion ....................................................................................................... 172 Carboxyl Carbon Data ........................................................................ 172 Ipso Carbon Data ................................................................................ 173 Asymmetry of 1 in Organic Solvent ................................................... 175 viii Conclusions .................................................................................................... 176 Works Cited .................................................................................................... 177 Chapter 3. Computational Study of the Base-catalyzed Decomposition of Malonic Anhydride ............................................................................................. 180 Introduction ...................................................................................................