Quantum Theory of the Chemical Bond

The present text is a rational analysis of the concept of the chemical bond by means of the principles of wave mechanics. The discussion of the material has been arranged so as to render its main content comprehensible for readers who may not have had pre"ious training in quantum mechanics. The text comprises three major parts. It begins with an exposition of the fundamental ideas. In this section the principles are reviewed from which de Broglie developed his mechanics; this allows the book to be read by chemistry majors and freshmen alike. However, we believe that it may also be of interest to university-and college teachers who must include certain aspects of quantum chemistry into their courses while being insufficiently familiar with the subject. It may even be of interest to science teachers in secondary schools. Finally, having been a witness to the evolution of these notions for over a quarter of a century, we present certain concepts from a particular point of view which might prove attractive to chemists of all kinds, perhaps even quantum chemists. The second, more technical part summarizes the methods of constructing wave functions that describe the electrons in molecules. This section can only be fully appreciated by those readers who are familiar with some aspects of the algorithms used in quantum mechanics.

I. Fundamental Ideas.- 1. Introduction.- 2. Wave Mechanics.- - The de Broglie Wave and the Particle.- - The Wave Equation.- - Stationary States.- - Wave Mechanics as a Set of Theorems.- 3. One-Electron Systems; the Hydrogen Atom and -Molecular Ion.- - The Hydrogen Atom According to Bohr’s Theory.- - The Hydrogen Atom in Wave Mechanics.- - The Hydrogen Molecular Ion.- - The Nature of the Energy of a One-Electron System.- 4. Two-Electron Systems; the Helium Atom and the Hydrogen Molecule.- - The Wave Mechanics of the System.- - The Helium Atom.- - First Appearance of the Concept of the Loge.- - The Hydrogen Molecule.- 5. Many-Electron Atoms; the Concept of Loge; Most Probable Configuration.- - Electron Spin and Pauli Principle.- - The Concept of Loge.- - The Most Probable Electron Configuration in an Atom.- 6. The Concept of the Chemical Bond.- - Short History; Definition of Vicinity of a Nucleus.- - Core Loges and Bond Loges.- - The Differential Density in Some Diatomic Molecules.- - Saturated Molecules; the Systematics of Additive Molecular Properties; Isomerization Energy.- - Covalent Bond; Coordinative Bond.- - Electron-Deficient Molecules; Molecules with Excess Electrons; Localized and De-localized Bonds.- 7. The Basis of Stereochemistry.- - Single Bonds and the Concept of the Lone Pair.- 8. Intermolecular Forces.- - The Energy of a System of Electrons and the Concept of the Supermolecule.- - Long-Range Intermolecular Forces.- - Short-Range Intermolecular Forces.- II. Survey of Computational Techniques.- 9. The Independent-Electron Model; the Non-Invariant Concept of Orbital.- - The Non-Independency of the Electrons in the Independent-Electron Model.- - The Non-Invariant Nature of the Concept of Orbital.- - The Concept of Spin Orbital and the Consequences of the Pauli Principle for Its Application.- - The Non-Invariance of the Exchange Energy; the Definition of the Most-Localized Orbital.- 10. Improvement and Extension of the Independent-Electron Model.- - Variation Methods; the Concepts of Screening Effect and Self-Consistent Field.- - Configuration Interaction.- - Molecular Orbitals and the Approximation by a Linear Combination of Atomic Orbitals.- - Technical Foundations of the Theory of Loges.- 11. Methods for the Calculation of Wave Functions, Assuming that Electrons can be Localized; Loge Functions, Core Functions, Bond Functions.- - Loge Functions.- - Approximate Representation of Core Functions.- - The Representation of a Localized Bonding Loge.- - The Representation of Lone-Pair Loges.- - The Representation of De-localized Bonding Loges; ?–? Separation.- - Empirical and Semi-Empirical Methods.- III. Applications.- 12. The Method of the Molecular Diagram and the Structure of De-localized Bonds.- - Static Indices.- - Molecular Diagrams of Conjugated Hydrocarbons.- - Molecular Diagrams of Other Conjugated Molecules; Orientating Effect of Substituents and Hetero-Atoms.- - Graphite and the Metallic Bond.- 13. Chemical Equilibria; Biological and Pharmacological Applications.- - The Alkalinity of Conjugated Molecules in Their Electronic Ground State.- - The Alkalinity of Conjugated Molecules in the First Excited Electronic State.- - The Origin of Life on Earth; Evolution of the Species.- - Molecular Structure and Pharmacological Activity.- 14. Reaction Rates; Theoretical Prediction of New Reactions; Applications to the Aetiology of Cancer.- - The Theory of the Transition State.- - Molecules Reacting in the Ground State; Thermal Reactions.- - Photochemical Reactions.- - The Contribution of Quantumchemistry to Chemical Carcinogenesis.- Conclusion. Epistemological Considerations Regarding The Quantum Theory of the Chemical Bond.- - Towards an Epistemology of Quantum Theories.- - On the Epistemology of the Chemical Bond.- References.- Index of Subjects.