Determination of the dihedral angle of the monoanion of succinic acid in aprotic media

A value of 74(+/-4) degrees was determined from NMR-observed dipolar couplings for the rotational dihedral angle of the monosuccinate anion in an aprotic liquid-crystal solution of the gauche conformation of tetraoctylammonium monosuccinate. This value is in reasonable agreement with other, somewhat less definitive, evidence gleaned from isotropic vicinal proton-proton couplings of the essentially completely gauche preference of the monosuccinate anion in tert-butyl alcohol and aprotic solvents, such as DMSO and THF, and quantum computations for the monoanion in THF.