Protonation behaviour of N,N'-piperazine-dipropionic acid

摘要

The overall protonation constants of N,N'-piperazine-dipropionic acid(PDPA)were calculated with SUPERQUAD and PSE-QUAD computer programs,at 25 and 37°C and an ionic strength of 0.1 mbl dm~(-3)(KCl).There is a good agreement 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_L=2.0716 mmol dm~(-3)at 25°C.A two-step deprotonation mechanism is proposed.In the first step the deprotonation occurs to the carboxyl group and in the second step it is the nitrogen atom of the piperazine ring which undergoes deprotonation.