An 11B nuclear magnetic resonance study of the reaction of the tetrahydroxyborate ion with polyhydroxy compounds

An 11B n.m.r. study of the formation of complexes between the tetrahydroxyborate ion, B(OH)–4, and various polyols has been carried out using ethane diol, propane-1,2-diol, propane-1,3-diol, glycerol, mannitol and sorbitol. The results show quite clearly that the polyols can form 1:1 and 1:2 borate–polyol complexes, and that the complexation is not limited to hydroxy groups on adjacent carbon atoms but can also involve those on alternate carbon atoms, although in the latter case the reaction is less favourable. Attempts have been made to calculate the equilibrium constants for the various equilibria in equimolar mixtures of polyol and borate ion.