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The Bell–Evans–Polanyi Principle and the regioselectivity of electrophilic aromatic substitution reactions

Author:
Wubbels, Gene G.
Source:
Tetrahedron letters 2015 v.56 no.13 pp. 1716-1719
ISSN:
0040-4039
Subject:
Lewis acids, activation energy, chemical reactions, chemical structure, enthalpy, regioselectivity, toluene
Abstract:
Relative activation energies of competing electrophilic aromatic substitution transition states are shown to correlate precisely with computed relative enthalpy changes leading to the corresponding σ complexes. The correlations manifest the Bell–Evans–Polanyi Principle, which may be summarized by the relationship, Ea=m(ΔH)+I. Close correlation occurs for a variety of reactions and reactivities, but correlation does not occur for nitration of toluene, a case known to be exceptional. The correlations imply that activation energies control regioselectivity, and that the properties of the competing transition states resemble those of the σ complexes.
Agid:
6025193