Optical rotations and conformations of (S)-propane-1,2-diol, D-threo-butane-2,3-diol and some alditols in aqueous and non-aqueous media
Empirical molecular rotation values for 1,2-gauche-substituents on a C–C unit are used additively to study the conformations of the two title diols in various solvents. Additivity breaks down for the unbranched carbon chain alditols and their primary and 2-deoxy derivatives. The deoxy compounds give characteristic rotations in water dependent on configuration, but almost independent of conformation. Likewise, alditols display almost zero rotation in water, independent of conformation, but have significant and differing rotations in non-aqueous media.