Abstract

Kinetics and Mechanism of OsO4 Catalysis in Acid Bromate Oxidation of Substituted 2-Azachalcones in Aqueous CH3COOH-H2SO4 Medium

Naseem*, Satla Gangakishan, S. Sharath Kumar Goud and E Venkata Ramana

Physical Chemistry Laboratory, Department of Pharmaceutical Chemistry, Telangana University-503322, Nizamabad, TS, INDIA.

DOI : http://dx.doi.org/10.29055/jccs/671

ABSTRACT

The kinetic and mechanism of OsO4 catalysis in acid bromate oxidation of substituted 2-Azachalcones have been studied in 50% (V/v) acetic acid - water – sulphuric acid medium at various temperatures. The reaction follows zero order kinetics in [Bromate] and [H+] fractional order in [substrate] and first order dependence on Os(VIII) catalyst. Varying the H+ the rate of the reaction is not altered. The Michaelis-Menten’s plot (1/kobs against 1/[S]) gives a positive intercept on y-axis support for the formation of the complex between the oxidant and substrate. A linear plot is observed with a positive slope by plotting of log k versus 1/D is suggesting that the reaction between two neutral molecules. The more negative value (-1.17) of ρ+ indicates the reaction is facilitated by more electron density at the reaction centre, and the rate of the reaction is increased by electron donating substituents and is decreased by the electron withdrawing substituents. Therefore, the different substituted 2-Azachalcones reactivity studied is p-OCH3 > p-CH3 > H > p-Cl. Thermodynamic activation parameters are evaluated.The products of Os(VIII) catalysis oxidation of 2-Azachalcone are identified as 1-picolinoyl-2arylethane-1,2-diol. Based on the above arguments the plausible mechanism proposed for the Os(VIII) catalyzed acid bromate oxidation of 2-Azachalone.

Keywords :Kinetics, catalyst, Azachalcones, mechanisms, oxidation.