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KMID : 1024520120210050585
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Journal of the Environmental Sciences
2012 Volume.21 No. 5 p.585 ~ p.596
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Dephosphorylation of Isopropyl phenyl-4-nitrophenylphosphinate (IPNPIN) onto 2-Alkylbenzimidazolide Anion in CTABr Micellar Solution
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Kim Jeung-Bea
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Abstract
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This study is mainly focused on micellar effect of cetyltrimethyl ammonium bromide(CTABr) solution including
alkylbenzimidazole(R-BI) on dephosphorylation of isopropyl-4-nitrophenylphosphinate(IPNPIN) in carbonate buffer(pH
10.7). The reactions of IPNPIN with R-BI? are strongly catalyzed by the micelles of CTABr. Dephosphorylation of IPNPIN
is accelerated by BI? ion in 10-2 M carbonate buffer(pH 10.7) of 4×10-3 M CTABr solution up to 89 times as compared with
the reaction in carbonate buffer by no benzimidazole(BI) solution of 4×10-3 M CTABr. The value of pseudo first order rate
constant(kψ) of the reaction in CTABr solution reached a maximum rate constant increasing micelle concentration. Such rate maxima are typical of micellar catalyzed bimolecular reactions. The reaction mediated by R-BI? in micellar solutions are obviously slower than those by BI?, and the reaction rate were decreased with increase of lengths of alkyl groups. It seems due to steric effect of alkyl groups of R-BI? in Stern layer of micellar solution. The surfactant reagent, CTABr, strongly catalyzes the reaction of IPNPIN with R-BI and its anion(R-BI?) in carbonate buffer(pH 10.7). For example, 4×10-3 M CTABr in 1×10-4 M BI solution increase the rate constant(kψ=98.5×10-3 sec-1) of the dephosphorylation by a factor ca.25, when compared with reaction(kψ=3.9×10-4 sec-1) in 1×10-4 M BI solution(without CTABr). And no CTABr solution, in 1×10-4 M BI solution increase the rate constant(kψ=3.9×10-4 sec-1) of the dephosphorylation by a factor ca.39, when
compared with reaction (kψ=1.0×10-5 sec-1) in water solution(without BI). This predicts that the reactivities of R-BI? in the
micellar pseudophase are much smaller than that of BI?. Due to the hydrophobicity and steric effect of alkyl group
substituents, these groups would penetrate into the core of the micelle for stabilization by van der Waals interaction with long alkyl groups of CTABr.
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KEYWORD
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CTABr, Micellar effect, Alkylbenzimidazole, Dephosphorylation
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