Controversy and complementarity in mechanistic organic chemistry. The transition state and structural theories reexamined

It is proposed that molecular phenomena may only be described within the framework of the Complementarity Principle (‘CP’), and that scientific controversy may originate in the essential incompatibility of complementary representations. Complementarity based on the temporal Uncertainty Principle leads to new insights into transition state theory, microscopic reversibility and the Curtin-Hammett Principle. An empirical application of the ‘CP’ to the structural theory leads to a revision of present concepts of ‘reaction dynamics’, with the Principle of Least Nuclear Motion (‘PLNM’) emerging as a general alternative to electronic theories of reactivity. In fact, it is argued that the ‘PLNM’ is a better basis for the Woodward-Hoffmann rules than is orbital symmetry. A more flexible approach to organic reaction mechanisms is thus indicated. Also, as the basis of the structural theory is fundamentally uncertain, and the present theory of X-ray diffraction apparently incompatible with the ‘UP’, a reinterpretation of the Bragg equation has been attempted.