13C shielding tensors in p-alkoxybenzenes

All ¹³C shielding tensors in p-dimethoxybenzene and p-diethoxybenzene were determined from powder patterns by means of proton enhanced nuclear induction spectroscopy. In contrast to alkyl-substituted benzenes the tensor sets differ considerably at the various aromatic sites and all tensor elements at the two nonequivalent ortho positions are influenced by the asymmetric substituent. In the solid state p-diethoxybenzene was found to have a planar or nearly planar conformation, like p-dimethoxybenzene.