Formation of neutral complexes of boric acid with 1,3-diols in organic solvents and in aqueous solution

From solubility measurements in organic media and extraction experiments, the values of the stability constants of neutral 1 : 1 complexes (HBL) formed between boric acid (HB) and 1,3-diols (L) have been obtained in aqueous solution (Kc(w)) and in organic solvents (Kc(s)). The values of the partition coefficients of the diols (PL) and the complexes (PHBL) between water and the organic solvents have also been calculated. Generally, the addition of a diol to an aqueous solution of borax is accompanied by a decrease of pH due to the prevailing formation of borate species but, in the case of 2-methyl-2,4-pentanediol, the pH increased, in agreement with the formation of a single neutral complex. It is shown that a modification of a previous potentiometric procedure yields simultaneously the values of the stability constants of the neutral and anionic complexes in aqueous solution.