Maximum Overlap Orbital Treatment of 13C–H Substituent Effects in the Halomethanes

Substituent effects on 13C–H coupling constants in the halomethanes have been calculated by the method of maximum overlap orbitals. The simplest choice of halogen orbitals (npσ) produces good agreement with observed values. Introduction of s character (based upon microwave data) and adjustment of ionic content of the C—halogen bond to give agreement with experiment leads to an over-all structure of these bonds that is in quite good agreement with the conclusions of Townes and Dailey.