OXIDATIVE KINETICS MECHANISM OF SUBSTITUTED CHALCONES BY IMIDAZOLIUM CHLOROCHROMATE

Abstract

The kinetics of oxidation of substituted chalcones by Imidazolium Chlorochromate (ICC) has been studied in 50% acetic acid-50% water medium. The order of the reaction is one with respect to oxidant, hydrogen ion and fractional order with respect to substrate concentration. The rate of the reaction has been conducted at five different temperatures. Thermodynamic parameters have been calculated. A good correlation is found to exist between logk1(308K) and Hammett constant(σ). For substituted chalcones, the electron withdrawing substituents are found to enhance the rate of the reactions and electron releasing substituents are found to retard the rate of the reaction. The rate data obeys the Hammett relationship. The order of reactivities with substituents is p-NO2 > m-NO2 > m-Br > m-Cl>p-Cl>p-Br > p-F > - H > m-CH3 > p-CH3 >p-OCH3. The Exner plot of k1(308k)versusk2(313k) is linear and isokinetic temperature is obtained. This supports that all the reactions under this investigation follow a common mechanism. The constant ΔG values are obtained for all the substituted compounds. It also indicates that the substituted compounds are oxidized by same mechanism. Cinnamic acid and Phenyl acetaldehyde was identified as the product of oxidation. Based on the kinetics results, a suitable mechanism has been proposed.