Kinetic Study for the Thermal Conversion of Creatine (C₄H₉O₂N₃) to Creatinine (C₄H₇ON₃)

Abstract

The thermal conversion of creatine (CR) to creatinine (CRN) in a phosphate buffer solution (pH6.5) at temperature ranging from 100 to 145°C was studied from a kinetic viewpoint. The heating process consisted of unsteady heating and cooling periods, and constant temperature heating periods. Since the conversion of CR to CRN progressed during the unsteady thermal process, heating time for it was corrected to the value of heating time under the constant temperature. When 60-76% of the CR converted to CRN, the conversion reached to an equilibrium. Therefore, the conversion of CR to CRN was regarded as a reversible reaction. The thermal conversion curve of CR to CRN calculated from a reversible lst order rate equation was best fitted into the measured conversion curve. The rate constants and activation energy for the forward reaction (CR→CRN) were estimated as 1.1-33.1x10^-4·s^-1 and 97.9 kJ·mol^-1, respectively. These kinetic parameters for the reverse reaction (CRN→CR) were estimated as 0.7-10.3×10^-4·s^-1 and 79.4kJ·mol^-1, respectively. Consequently the heat of reaction for this reversible reaction was estimated as 18.5kJ·mol^-1.