European Journal of Biomedical and Pharmaceutical Sciences

THERMODYNAMIC, KINETIC, MECHANISTIC AND SPECTROSCOPIC INVESTIGATION OF THIAMINE HYDROCHLORIDE (VITAMIN B1) OXIDATION BY VANDIUM (V), AN INSULIN MIMETIC COMPOUND AT LOW PH

J. Panda, S. P. Das* and A. K. Patnaik*

ABSTRACT

The kinetics of oxidation of Thiamine Hydrochloride (Vitamin B1) by vanadium (v) compound have been carried out by using spectrophotometric technique over the range 2.0≤ 105 [Vit B1] mol dm-3 ≤ 5.0, 1.7 ≤ pH ≤ 2.5 and temperature range 293 K ≤ T ≤ 318 K were run under pseudo – first order conditions. The rate of oxidation was found to be first order with respect to vitamin B1, and vanadium (v) concentration. This reaction is pH dependent. When pH increases 1.7 to 2.5, rate constant decreases whereas with decrease of dielectric constant of the medium rate constant increases. Ionic strength has no effect on such reaction. During electron transfer process thiamine hydrochloride forms a weak coordination complex with dioxovanadium (v) ion, hence inner-electron transfer reaction is suggested. Oxidation product was isolated and identified as thiochrome and vanadium (iv) which was supported by UV visible, FTIR and 1HNMR spectroscopy. Moderate values of activation parameters such as activation enthalpy H# = 37.67 + 6.82 kJmol-1, S# = 101.2 + 21.73 JK mol-1 activation free energy G# = 67.86 kJmol-1 are favourable for electron transfer process. The negative value of S# indicates that transition state is more ordered than reactants.

Keywords: Kinetic, redox reaction, vitamin B1, vanadium (v) complex, spectrophotometry, product thiochrome, activation parameters.