Study of dimethyl-substituted benzene derivatives by 13C nuclear magnetic resonance spectroscopy and INDO MO calculations

A 13C n.m.r. investigation of some substituted dimethyl benzenes is reported. The spectral analysis were carried out by the iterative Laocoon III and a spin-simulation program furnished carbon–proton coupling constants that have been rationalized with the aid of the FPT–INDO MO calculations. The angular dependences of the calculated 3JC,CHO and 1JCHO coupling constants have been analysed and the preferred conformations are discussed.