Spectroscopic and kinetic studies on the interaction of ketoconazole and povidone drugs with DDQ

The kinetics and mechanism of the interaction between 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and ketoconazole and povidone drugs has been investigated spectroscopically. In the presence of large excess of donor, the 1:1 CT complex is transformed into a final product, which has been isolated and characterized by FT-IR and GC-MS techniques. The rate of formation of product has been measured as a function of time in different solvents at three temperatures. The thermodynamic parameters, viz. activation energy, enthalpy, entropy and free energy of activation were computed from temperature dependence of rate constants. Based on the spectro-kinetic results a plausible mechanism for the formation of the complex and its transformation into final product is presented and discussed. (C) 2007 Published by Elsevier B.V.