Chemical Reactions in Surfactant Solutions(Ⅲ). Nucleophilic and Micellar Catalyses on Hydrolysis of an Organic Phosphate by Sodium 2-Alkylbenzimidazole-5-sulfonates in Aqueous and CTABr Solutions

계면활성제 용액속에서의 화학반응(제3보) 유기인산 에스테르의 가수분해반응에 미치는 2-알킬벤즈이미다졸-5-술포네이트의 친핵적 및 미셀 촉매효과

  • Published : 19901100

Abstract

Dephosphorylation of p-nitrophenyldiphenylphosphate(p-NPDPP) mediated by anions of sodium 2-alkylbenzimidazole-5-sulfonate(R-BI-SO$_3$Na) in CTABr micellar solutions are obviously slower than that by anion of sodium benzimidazole-5-sulfonate(BI-SO$_3$Na), and the reation rates were decreased with increase of lengths of alkyl groups. This presents a striking contrast to the reactions in aqueous solutions without added CTABr, of which the reaction rates are on approximately same levels. It seems due to steric effect of alkyl groups of R-BI$^-$SO$_3$Na in the Stern layer of micelle, and it is supported by measured activation parameters(△H$^\neq$/TEX>, △G$^\neq$/TEX> and △S$^\neq$/TEX>) of the reactions in aqueous and micellar solutions. In addition to nucleophilic ability of benzimidazole moiety of R-BI$^-$SO$_3$Na on the reactions, these compounds with long alkyl groups(nonyl to pentadecyl) are micellized for themseleves, and increase the reaction rates due to their micellar catalyses in aqueous solutions, not including CTABr.

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References

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