First and Second Dissociation Constants of Deuterio-o-Phthalic Acid in D2O from 5 to 50 deg C

Article abstract of DOI:10.1007/BF00644891

The first and second dissociation constants of deuterio-o-phthalic acid in deuterium oxide have been determined by the emf method over the temperature range of 5 to 50 deg C.The pD values for potassium deuterium phthalate have been calculated from these two constants and experimentally verified.The thermodynamic properties for the dissociation of deuterio-o-phthalic acid have been evaluated.At 25 deg C, these values in the molality scale are: pK_1A = 3.505, pK_2A = 5.890, and pD = 4.518.From K_1A and K_2A, respectively: ΔG^o = 20.003, 33.582 kJ-mol^-1; ΔH^o = 2.851, 2.208 kJ-mol^-1; ΔS^o = -76.7, -105.2 J-mol^-1-K^-1; and ΔC^o_p = -52.7, -315.6 J-mol^-1-K^-1.The isotope effect is discussed.