Medium and alkyl chain effects on the protonation of dicarboxylates in NaCl(aq) and Et4NI(aq) at 25°C

In this work we report the thermodynamic parameters for the protonation of a homologous series of linear dicarboxylates having the molecular formula, HOOC-(CH2)(n)-COOH, with n = 0 - 7 ( n = 0 oxalate; n = 1 malonate; n = 2 succinate; n = 3 glutarate; n = 4 adipate; n = 5 pimelate; n = 6 suberate; n = 7 azelate). The investigation was performed by potentiometry (H+- glass-electrode) at 25degreesC in different ionic media and different ionic strengths (NaCl: 0 less than or equal to I [mol-L-1] less than or equal to 4.9; Et4NI: 0 less than or equal to I [mol-L-1] less than or equal to 1). General equations for the dependence on ionic strength of the thermodynamic parameters were used, and the relative parameters are reported. The influence of the length of the alkyl chain on protonation constants and on their dependence on ionic strength is discussed. Some recommended values of protonation constants are reported by considering present results and literature ones.