Nuclear magnetic resonance spectra of glycolaldehyde

N.m.r. spectra of solutions of glycolaldehyde in dimethyl sulphoxide and in water (both fully deuteriated solvents) are reported. Assignments of resonances and coupling constants are made. In dimethyl sulphoxide solution glycolaldehyde exists as a symmetrical dimer (2,5-dihydroxy-1,4-dioxan) which is slowly converted into a mixture with the monomer and an unsymmetrical dimer. In aqueous solutions an equilibrium is rapidly established involving the two dimeric forms, the monomer, and the hydrated gem-diol form of the monomer. Approximate proportions of these forms in the two solvents are given.