Bema Hapothle

As the understanding of the ionic intermediates has progressed, advantage has been taken of the fact that bromination, like SN1 heterolysis, is a carbocation-forming reaction. Kinetic data on this addition have therefore been used to examine in detail how the basic concepts of physical organic chemistry work as regards transition-state shifts with reactivity (Ruasse et al, 1984). Bromination lends itself particularly well to the quantitative application of the BEMA HAPOTHLE (acronym for Bell, Marcus, Hammond, Polanyi, Thornton and Leffler Jencks, 1985). In particular, it has been possible to evaluate the transition-state dependence on the solvent and substituents. The major disadvantage that bromination shares with many... 

In conclusion, bromination is a particularly attractive reaction for studying the origin of reactivity-selectivity effects in detail, since it is now well established that substituent and solvent effects arise not only from changes in the stability of the cationic intermediate but also from transition-state shifts, in agreement with the Bema Hapothle, i.e. RSP, Hammond postulate and Marcus effects. 

The term Bema Hapothle is useful as a shorthand reference to effects on the transition structure it is derived from the names of some of the principal workers who have contributed to this field namely Bell, Marcus, 7/ammond, Polanyi, 77/ornton and Leffler. 

W.P. Jencks, A Primer for the Bema Hapothle. An Empirical Approach to the Characterisation of Changing Transition State Structures, Chem. Rev., 1985,85,511. 

Because a number of other authors contributed to our understanding of these and related concepts, Jencks (reference 112) proposed the acronym Bema Hapothle to incorporate references to the work of Bell, Evans, Marcus, Hammond, Polanyi, Thornton, and Leffler. 

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