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Substitutent effects in monosubstituted benzenes: Semi‐empirical SCF studies of the Hammett constants
Author(s) -
Monaco Regina R.,
Gardiner William C.
Publication year - 1995
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610081002
Subject(s) - chemistry , computational chemistry , hammett equation , hamiltonian (control theory) , molecule , ring (chemistry) , force constant , thermodynamics , reaction rate constant , organic chemistry , kinetics , quantum mechanics , physics , mathematical optimization , mathematics
Abstract Semi‐empirical SCF calculations using the AM1 Hamiltonian were shown to account for the Hammett σ constants and other properties of a representative series of 22 monosubstituted benzenes in terms of the atomic charges at the ipso , ortho , meta and para positions. The trends of the correlations with experimental σ constants were found to follow the normal expectations of physical organic chemistry. Additional support for the AM1 charge distributions was obtained in correlations with the 13 C chemical shifts of 12 of the test molecules. On the other hand, no correlations were found between σ constants and computed force constants for bending peripheral H atoms out of the plane of the aromatic ring, supporting the view that Hammett σ constants reffect charge distributions and not secondary effects expressed in the stiffness of bonds.