Unified theory basic applications

This text has grown out of the monograph Propagators in Quantum Chemistry by J. Linderberg and Y. Ohrn, Academic Press, London, 1973, which has been out of print for some time. The content is revised to take into account some of the considerable literature in the intervening years by many workers in the field. However, this is not intended as a review of the theory and application of propagators, but rather an attempt to present the theory and the basic approximations in a unified manner with some illustrative applications. The material is presented from our own perspective, and we apologize for any omissions of references to important work in the field. 

The result was published in 1939 as The Nature of the Chemical Bond and the Structure of Molecules and Crystals An Introduction to Modern Structural Chemistry. It would become the most important Baker lecture book ever printed, and one of the most-cited scientific texts in history. In a very basic way, this book changed the course of chemistry. For the first time, the discipline was explained not as a collection of facts tied together by practical application in the laboratory but as a field unified by an underlying physical theory Pauling s quantum-mechanical ideas about the chemical bond. By showing how the new physics explained the chemical bond, how those bonds explained the structure of molecules, and how molecules structure explained their behavior, Pauling showed for the first time, as the Nobel Prize-winner Max Perutz said, that chemistry could be understood rather than memorized. ... 

Counting the isomers arising by addition to, or substitution in, a basic framework is a mathematical problem with many practical applications in chemistry. In classical organic chemistry, for example, the number of derivatives of a compound was often cited as proof or disproof of structure. Point group theory that uses concepts familiar to most chemists and is easy to apply when the number of addends/substituents is small provides a unified method for deciding, for example, the number of dihydrides C70H2 of fullerene C70, or the number of trihalo-derivatives C2oHi7FClBr of dodecahedrane. All that is needed to determine such matters is the availability of the permutation character. Ter, of the atoms in the parent molecule. 

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