The dependence of vicinal proton–proton coupling constants on dihedral angle and substituents

Abstract

Extended Hückel theory molecular orbital calculations of the vicinal proton–proton coupling constants in 1,1- and 1,2-difluoroethanes are presented and compared with experimental results. Equations, describing the angular dependence of vicinal couplings in substituted CH–CH fragments, are formulated on the basis of the MO calculations. Empirical parameters for these equations are derived from a least-squares treatment of a large number of experimental coupling constants.