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High-resolution double resonance methods have been employed to study the anisotropic 13C chemical shifts in single crystals of hexamethylbenzene, hexaethylbenzene, and pentamethylbenzene. Methyl and methylene shifts have small anisotropies. Shielding of the ring carbons is a maximum when the magnetic field is normal to the ring and a minimum when it lies along the bond to the substituent. The hexaethylbenzene molecule is shown to have D3d symmetry. The orientations of the two molecules in the unit cell of pentamethylbenzene are determined.
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Paušak et al. (1974) studied this question.
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