Carbon-13 chemical shielding tensors in acetic acid

High resolution double resonance methods have been employed to study the anisotropic 13C chemical shifts in a single crystal of acetic acid. The principal values in ppm relative to an external reference of liquid benzene are -136+-2, -52+-2 and 24+-2 for the carboxyl carbon and 89+-2, 102+-2 and 123+-2 for the methyl carbon. The most shielded element of the carboxyl tensor is found perpendicular to the molecular plane, the least shielded element makes an angle of 470 with the C-C bond direction. The most shielded element of the methyl tensor is found in the molecular plane, making an angle of 190 with the C-C bond direction. (Auth.)