1H NMR spectra and conformations of propane-1,2-diol, meso- and racemic butane-2,3-diols, and some alditols in non-aqueous media

The solvent change low polar→protic→very polar aprotic causes a progressive change in the conformation of the three title diols towards the conformer with the two C–O bonds trans. Alditols in deuterium oxide have each hydroxymethyl group with the C–O bond extending the chain as the main conformer. In polar aprotic solvents the main conformer has the C–O bond trans to the adjacent C–O bond. The carbon chain conformation can be somewhat different in the two solvent types.