Author(s): D. Raga Sudha, G. Nageswara Rao and P. Vani*
The kinetics of oxidation of L-serine(Ser) by periodate(Per) in presence of an anionic surfactant, sodium dodecyl sulphate(SDS) was studied spectrophotometrically at 280 nm in perchloric acid medium at 303 K. The reaction exhibited first order dependence on [Per], [Ser] and [H+ ]. It was found that increase in [SDS] causes an increase in rate indicating that the reaction was catalysed by anionic micelles. The critical micelle concentration(CMC) for SDS was determined in 0.12 mol dm-3 ionic strength in presence of oxidant by surface tension measurements and found to be 1.0 x 10-4 mol dm-3 . The rate-[surfactant] profile shows a limiting behaviour indicative of unimolecular rate-determining reaction in the micellar pseudo-phase. 2-hydroxy acetaldehyde was identified to be the main product of oxidation by IR-spectroscopy. The activation parameters were computed using linear least squares method and the values of Ea and ΔS# are found to be 21.39 ± 1.64 kJ mol-1 and -312 ± 4.67 JK-1 mol-1 respectively.