The use of partially restricted molecular orbitals to investigate transmission mechanisms of spin–spin coupling constants. III—an INDO study of long‐range FH couplings in fluorinated derivatives of toluene

Transmission mechanisms of long‐range FH couplings in several fluorinated derivatives of toluene are analysed carrying out partially restricted molecular orbital calculations at the INDO level of approximation. All π‐components follow the A+B sin²θ dependence, with the dihedral angle defined by the exocyclic CH (or CF) bond and the aromatic ring plane. Four‐ and five‐bond couplings show an important σ‐component, which follows the known zig‐zag rule. Both σ‐ and π‐contributions show a conspicuous insensitivity to fluorine ring substitution. Moreover, four‐bond couplings present an important through‐space component, which is negative for a cis arrangement. A sign inversion is found at a dihedral angle between 70° and 80°, which is interpreted as indicating that several through‐space mechanisms are operating. Copyright © 1982 Heyden & Son Ltd.

Duke Scholars

Author Julio Cesar Facelli Biostatistics & Bioinformatics, Division of Translational Bi ...