https://doi.org/10.1351/goldbook.H02734
The hypothesis that, when a
transition state
leading to an
unstable
reaction intermediate
(or product) has nearly the same energy as that intermediate, the two are interconverted with only a small reorganization of molecular structure. Essentially the same idea is sometimes referred to as 'Leffler's assumption', namely, that the
transition state
bears the greater resemblance to the less
stable
species (reactant or
reaction intermediate
/product). Many text books and physical organic chemists, however, express the idea in Leffler's form, but attribute it to Hammond. As a corollary, it follows that a factor stabilizing a
reaction intermediate
will also stabilize the
transition state
leading to that intermediate. The acronym 'Bemahapothle' (Bell, Marcus, Hammond, Polanyi, Thornton, Leffler) is sometimes used in recognition of the principal contributors towards expansion of the original idea of the Hammond postulate.
See also:
More O'Ferrall–Jencks diagram
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1119 [Terms] [Paper]