Because most chemical reactions, by definition, cannot avoid breaking of bonds, weakly bonded species exist fleetingly in almost every chemical change. Historically, chemical quantum mechanics was aimed at explaining the nature of strong bonds. The theory involved a number of approximations to the full solution of the Schrödinger equation. The study of non‐Kekulé molecules provides an opportunity to test whether modern quantum chemical computations are competent to deal with the nature of molecules with very weak bonds. †To contact the author, (...) please write to: Department of Chemistry, Yale University, New Haven, CT: 06520‐8107; e‐mail: [email protected]. (shrink)

What is it that turns a new observation into a true scientific discovery? And who may claim the credit? Theoreticians of science, the foremost thinkers of their times among them, have tried to answer these fundamental questions about the nature of scientific progress and discovery. With clear insight and the chemical as well as philosophical wisdom gained from over fifty years as a practising chemist, Jerome Berson puts their theories to the test. The development of chemistry into a "modern" science (...) during the last two centuries provides him with ample cases to illustrate the way scientific progress really happens. Kekul?'s struggle to arrive at a structure for benzene, the paradigm change that was necessary to accept the reality of molecular rearrangements, and other episodes are retold here from the philosopher's as well as from the practitioner's perspective, shedding light on the way scientists think and act. Berson's account of the rather unphilosophical way in which scientific discoveries are made includes the realization that even a false hypothesis, such as Woodward's ideas about the biosynthesis of strychnine, may help rather than hinder scientific progress. Scientists of all ages, as well as many non-scientists, will find this a highly readable and unusual book. (shrink)

Many theories require empirical patches or ad hoc assumptions to work properly in application to chemistry. Some examples include the Bohr quantum theory of atomic spectra, the Pauli exclusion principle, the Marcus theory of the rate-equilibrium correlation, Kekule’s hypothesis of bond oscillation in benzene, and the quantum calculation of reaction pathways. Often the proposed refinements do not grow out of the original theory but are devised and added ad hoc. This brings into question the goal of constructing theories derived from (...) first principles and the concept of ranking the merit of theories according to their freedom from empirical contamination. (shrink)