DISTRIBUTION OF HYDROGEN ISOTOPES BETWEEN H2PO4- AND WATER IN PARTIALLY DEUTERATED SOLUTIONS

Using nmr, the distribution of hydrogen isotopes between water and diacid phosphate in partially deuterated aqueous solution has been determined. When coupled with the known isotopic ratios of acid dissociation constants of phosphoric acid and diacid phosphate, and certain assumptions, this permits the distribution to be evaluated for phosphoric acid and monoacid phosphate as well. The first two are reasonable and permit a reasonable approximation of the acid dissociation constant of phosphoric acid in isotopically mixed solvent. That for monoacid phosphate is unreasonable, and it is concluded that ΔFo of transfer of this species from H2O to D2O is probably not zero.