Hammond's postulate

Hypothesis in physical organic chemistry

Hammond's postulate (or alternatively the Hammond–Leffler postulate), is a hypothesis in physical organic chemistry which describes the geometric structure of the transition state in an organic chemical reaction. First proposed by George Hammond in 1955, the postulate states that: If two states, as, for example, a transition state and an unstable intermediate, occur consecutively during a reaction process and have nearly the same energy content, their interconversion will involve only a small reorganization of the molecular structures. Therefore, the geometric structure of a state can be predicted by comparing its energy to the species neighboring it along the reaction coordinate.

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