Mechanistic investigation of the oxidation of vitamin B1 with sodium N-chlorobenzenesulfonamide in presence of ruthenium(III)catalyst in hydrochloric acid medium:a kinetic approach

摘要

The oxidative cleavage of vitamin B1(thiamine hydrochloride,THM)with sodium N-chloro-benzenesulfonamide(chloramine-B,CAB)has been kinetically investigated in HCl medium in presence of ruthenium(III)catalyst at 308 K.The oxidation reaction follows the rate law,-d[CAB]/dt=k[CAB][Ru(III)][H~+][THM]~a[Cl~-]~b,where a and b are less than unity.Variation of ionic strength of the medium and addition of the reaction product,benzenesulfon-amide(BSA)had no significant effect on the reaction rate.The change in relative permittivity of the medium affected by changing the solvent composition with acetonitrile has been studied.The stoichiometry of the reaction was found to be 1:1,and N-[(4-amino-2-methylpyrimidine-5-yl)methyl]benzensulfonamide and 2-(4-methylthiazol-5-yl)ethanol were identified as the oxidation products of vitamin B1.The reaction constants involved in the mechanism were computed.The reaction was studied at different temperatures and the overall activation parameters have been evaluated.C6H5SO2NHCl has been postulated as the reactive oxidizing species.The observed results have been explained by plausible mechanisms and the relative rate laws have been deduced.