The influence of pH and temperature on the degradation kinetics of 4-methoxy-2-[3-(4-phenyl-1-piperazinyl)]propyl-2,3-dihydro-6-methyl-1,3-dioxo-1H-pyrrolo[3,4-c] pyridine in aqueous solutions.

ABSTRACT

The pH-rate profiles for hydrolysis of 4-methoxy-2-[3-(4-phenyl-1-piperazinyl)]propyl-2,3-dihydro-6-methyl-1,3-dioxo-1H-pyrrolo[3,4-c] pyridine (H) at 333, 343, 353 and 363 K over the pH range 0.4-5.0 was investigated. The decomposition was followed by the HPLC method (LiChrosorb 100 RP-18 column 250 x 4.0 mm I.D., dp = 5 microm; mobile phase acetonitrile-phosphate buffer (pH = 2; 0.01 mole/L) (45 55, v/v or 30 70, v/v). The pH-rate profile indicated specific acid- and base-catalysed reactions as well as spontaneous water-catalysed degradation of two molecules of II (as a dication and monocation). The ionic strength effect, the pKa value (2.4; 6.2), the pHmin value (2.1) and thermodynamic parameters of the reaction (energy and enthalpy of activation and the frequency coefficient for the specific rate constants) were determined.