This study was performed to explain a regiospecific demethylation of 3-alkyl-1, 2- dimethoxybenzenes. PRDDO-MO calculations show that the low-energy conformation of the carbon of a methoxy group having two ortho neighbors on a benzene ring is located out of the plane of the aromatic ring, whereas a methoxy group with only one ortho neighbor executes restricted rotation in the plane of the ring. The carbon portion of the methoxy ...