Effect of cationic micellar aggregates on the kinetics of oxidation of aminoalcohols by N-bromosuccinimide in alkaline medium.
The kinetics of oxidation of some aminoalcohols (AA), viz. ethanolamine, diethanolamine, and triethanolamine, by N-bromosuccinimide (NBS) in alkaline medium has been investigated in the absence as well as in the presence of cetyltrimethylammonium bromide (CTAB), a cationic surfactant. The reaction always followed a first-order dependence of rate on NBS, while the order in each AA and alkali was found to decrease from unity to zero at higher [AA] and [OH-], respectively. The reaction is strongly catalyzed by CTAB even before the critical micelle concentration (CMC) of CTAB. However, the observed rate constants attained constancy at higher [CTAB] (>CMC of CTAB). The premicellar kinetics has been rationalized in the light of the Piszkiewicz positive cooperativity model [J. Am. Chem. Soc. 99 (1977) 1550]. The binding constants between the reactants and the surfactant have also been evaluated using the Raghvan and Srinivasan model [Proc. Ind. Acad. Sci. 98 (1987) 199], which is applicable to bimolecular micellar catalyzed reaction and predicts constancy in the observed rate constant at higher [surfactant]. The binding constants obtained by both the models are in good agreement.
Pandey
Shalini
S
Department of Chemistry, H.B. Technological Institute, Kanpur 208 002, India.
Upadhyay
Santosh K
SK
D000438:Alcohols / Q000737:chemistry*; D000468:Alkalies / Q000737:chemistry*; D001974:Bromosuccinimide / Q000737:chemistry*; D002412:Cations; D007700:Kinetics; D008823:Micelles; D010084:Oxidation-Reduction; D013501:Surface-Active Agents / Q000737:chemistry
D000438:Alcohols; D000468:Alkalies; D002412:Cations; D008823:Micelles; D013501:Surface-Active Agents; D001974:Bromosuccinimide