Protonation Behavior of N, N’-Piperazine-Dipropionic Acid

The overall protonation constants of N,N’-piperazine-dipropionic acid (PDPA) were calculated with Super quad and Psequad computer programs, at 25C and 37C and an ionic strength of 0.1 M (KCl). There is a similitude between the values calculated with the two programs. The obtained values were checked by a simulation titration curve and by the protonation (observed and calculated) curves for C = 2.0716 mmol dm at 25C. It was proposed a deprotonation scheme in two steps. In the first step the deprotonation occurs to the carboxyl group and in the second one the deprotonation process takes place to the nitrogen atom of the piperazine ring.