CATALYTIC ACTIVITY OF CETYLTRIMETHYLAMMONIUM BROMIDE (CTAB) IN THE REACTION OF NINHYDRIN AND ZINC GLYCYLTYROSINE COMPLEX

Mohd. Akram, Dileep Kumar, . Kabir-ud-Din

Abstract


The kinetics of interaction between ninhydrin and zinc-dipeptide (glycyl-tyrosine),  [Zn(II)-Gly-Tyr]+ complex have been studied in aqueous and in micelles formed by the cationic surface active material, cetyltrimethylammonium bromide (CTAB) at 80 °C and pH 5.0. The reaction follows first- and fractional- order kinetics with respect to [Zn(II)-Gly-Tyr]+ and [ninhydrin], respectively, both in the absence and presence of cationic CTAB micelles. The catalytic role of [CTAB] can be related to the extent of incorporation or association of the [Zn(II)-Gly-Tyr]+complex and ninhydrin into the micelles. CTAB micelles decrease the activation enthalpy and make the activation entropy less negative. The micellar catalysis is explained in terms of the pseudo-phase model of the micelles.  Binding constants KS for [Zn(II)-Gly-Tyr]+ and KN for ninhydrin with micelles are calculated with the help of observed kinetic data.


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DOI: http://dx.doi.org/10.17628/ecb.2013.2.801-806

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