Ho Ho-On. / Thesis submitted in: August 2004. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references. / Abstracts in English and Chinese. / Thesis Committee --- p.i / Abstract --- p.ii / Acknowledgements --- p.iv / Table of Contents --- p.v / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- The Gaussian-3 Method --- p.1 / Chapter 1.2 --- The G3 Method with Reduced MΦller-Plesset Order and Basis Set --- p.2 / Chapter 1.3 --- Calculation of Thermodynamical Data --- p.2 / Chapter 1.4 --- Remark on the Location of Transition Structures --- p.3 / Chapter 1.5 --- Natural Bond Orbital (NBO) Analysis --- p.3 / Chapter 1.6 --- Scope of the Thesis --- p.4 / Chapter 1.7 --- References --- p.4 / Chapter Chapter 2 --- The Important Basic Concepts of Ab Initio Calculations and Their Application to Pericyclic Reactions --- p.6 / Chapter 2.1 --- Potential Energy Surfaces --- p.6 / Chapter 2.2 --- Ab Initio Method --- p.6 / Chapter 2.2.1 --- Basic Sets --- p.7 / Chapter 2.2.2 --- Correlation Methods --- p.8 / Chapter 2.3 --- Pericyclic Reaction --- p.10 / Chapter 2.4 --- The Perturbation Theory of Reactivity --- p.10 / Chapter 2.5 --- References --- p.11 / Chapter Chapter 3 --- Ab Initio Study of the Cycloaddition Reaction between Ethylene and Butadiene as well as That between Ethylene and Hexatriene --- p.13 / Chapter 3.1 --- Introduction --- p.13 / Chapter 3.2 --- Methods of Calculation --- p.15 / Chapter 3.3 --- Results and Discussion --- p.15 / Chapter 3.3.1 --- Reaction between ethylene and butadiene --- p.30 / Chapter 3.3.2 --- Reaction between ethylene and hexatriene --- p.34 / Chapter 3.3.3 --- Electrocyclic reaction of hexatriene --- p.37 / Chapter 3.4 --- Conclusion --- p.40 / Chapter 3.5 --- References --- p.41 / Chapter Chapter 4 --- A G3(MP2) Study on the Electrocyclic Reactions of [12]annulene --- p.43 / Chapter 4.1 --- Introduction --- p.43 / Chapter 4.2 --- Methods of Calculation --- p.44 / Chapter 4.3 --- Results and Discussion --- p.45 / Chapter 4.4 --- Summary --- p.51 / Chapter 4.5 --- Conclusion --- p.52 / Chapter 4.6 --- References --- p.52 / Chapter Chapter 5 --- A G3(MP2) Study on the Cycloaddition Reactions between Ethylene and Azines as well as Other Related Systems --- p.54 / Chapter 5.1 --- Introduction --- p.54 / Chapter 5.2 --- Methods of Calculation --- p.55 / Chapter 5.3 --- Results and Discussion --- p.55 / Chapter 5.3.1 --- Addition of ethylene to azines --- p.55 / Chapter 5.3.2 --- "Addition of ethylene to quinolene, isoquinolene and 1,8-naphthyridine" --- p.64 / Chapter 5.4 --- Conclusion --- p.70 / Chapter 5.5 --- References --- p.70 / Chapter Chapter 6 --- Conclusion --- p.72 / Appendix A Energetic and Bonding Investigation of Phosphabenzene and Arsabenzene: A Gaussian-3 Study --- p.73 / Chapter A.1 --- Introduction --- p.73 / Chapter A.2 --- Methods of Calculation --- p.73 / Chapter A.3 --- Results and Discussion --- p.74 / Chapter A.4 --- Conclusion --- p.77 / Chapter A.5 --- References --- p.77 / Appendix B Energetic and Bonding Study of Hexamethylenetetramine (HMT) and Fourteen Related Cage Molecules: A G3(MP2) Investigation --- p.79 / Chapter B.1 --- Introduction --- p.79 / Chapter B.2 --- Methods of Calculation --- p.80 / Chapter B.3 --- Results and Discussion --- p.80 / Chapter B.4 --- Conclusion --- p.87 / Chapter B.5 --- References --- p.87 / Appendix C The Gaussian-3 Theoretical Models --- p.89 / Chapter C.1 --- The G3 Theory --- p.89 / Chapter C.2 --- The G3(MP2) Theory --- p.90 / "Appendix D Calculation of Enthalpy at 298 K, H298" --- p.91