The Calculation of directly bonded 13C-H and 13C-13C coupling constants using delocalized molecular orbital theory

Abstract

The Pople-Santry theory of coupling in σ-electron systems lias been applied to directly bonded CH and CC coupling constants. Calculations on normal hydrocarbons, e.g. CH4, C2H6, C2H4, C2H2, show that the theory can give a satisfactory explanation of such coupling constants, although the values are sensitive to the parameters used in the calculation. The theory has been applied with varying success to the larger hydrocarbons methylacetylene, butadiene and benzene, and to the strained molecules cyclopropane and ferrocene. No difficulty arises in applying the theory to hetero-atomic systems (pyridine and pyrimidine) and the results are quite satisfactory.