A maximum overlap orbital calculation of 13C-H coupling constants in the vinyl halides

Abstract

The method of maximum overlap orbitals (MOO) has been employed to calculate all of the 13C - H coupling constants in the vinyl halides. The results indicate that values at the Β position depend primarily on mesomeric content of each halide, whereas the α couplings are predominately influenced by the nature of the C - X bond. By using only pure p-orbitals for X = C1, Br and I, the observed α couplings are predicted to within one cps, but in the fluoride ∼ 25% s-character is required to obtain satisfactory agreement. The results of these calculations are compared with those obtained for the methyl halides, and are also discussed in relation to relevant bonding inferences derived from microwave data.