Nonionic Micellar Catalyzed Oxidation of Vitamins by Chloramine-T in HClO₄ Medium: A Kinetic Study

Abstract

The kinetics of oxidation of vitamin B₁ (thiamine hydrochloride) and vitamin B₆ (pyridoxine hydrochloride) by chloramine-T (CAT) in perchloric acid medium and in presence of a non ionic surfactant (Triton x-100) have been investigated. A catalytic effect of the nonionic micelle on the rate of oxidation has been observed and rate is found to be proportional to 7lcub;k′ + k″ [Triton x-100]}, where k′ and k″ are the rate constants in absence and presence of surfactant, respectively. The rate shows a first-order, a fractional order and a zero order dependence on [Chloramine-T]_o, [Vitamin]_o and [H⁺]₀, respectively in absence as well as in presence of surfactant. A mechanism involving association/binding between the oxidant and the surfactant micelle, which is supported by spectrophotometric evidence has been proposed. The binding parameters have also been evaluated using a pseudo-phase kinetic model.

Keywords:

• Chloramine-T oxidation
• kinetics
• micellar catalysis
• oxidations of vitamins

N. K. is thankful to DST, New Delhi for financial assistance of the project.

Notes

[Vitamin] = 2 × 10⁻² mol dm⁻³ and [Tx-100] = 4 × 10⁻³ mol dm⁻³ CMC of Tx-100 = 1.7 × 10⁻⁴