Premicellar Accelerated Decarboxylation of 6-Nitrobenzisoxazole-3-carboxylate Ion and Its 5-Tetradecyloxy Derivative

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• 作者：Lucia Brinchi ; Pietro Di Profio ; Raimondo Germani ; Laura Goracci ; Gianfranco Savelli ; Nicholas D. Gillitt ; Clifford A. Bunton
• 刊名：Langmuir
• 出版年：2007
• 出版时间：January 16, 2007
• 年：2007
• 卷：23
• 期：2
• 页码：436 - 442
• 全文大小：85K
• 年卷期：v.23,no.2(January 16, 2007)
• ISSN：1520-5827

文摘

Didodecyldialkylammonium chloride and bromide (alkyl = Me, Et, n-Pr, n-Bu) accelerate the spontaneousdecarboxylation of 6-nitrobenzisoxazole-3-carboxylate ion, 1,H, and its 5-tetradecyloxy derivative, 1,OTD. With mostof these surfactants, first-order rate constants, k_obs, go through maxima in very dilute surfactant and then decrease andgo through minima as association colloids form. These phenomena are not explicable in terms of substrate-inducedmicellization. However, k_obs increases in the N-alkyl sequence Me < Et < n-Pr < n-Bu, as is typical of decarboxylationsin association colloids of single-chain surfactants. Reaction in premicelles is accelerated by an initial increase in 1,H.The factors that control relative rates of spontaneous reactions in premicelles and in the association colloids, inparticular, depletion of water at the reaction center and association of substrate and quaternary ammonium centers,are discussed with respect to the roles of substrate and surfactant hydrophobicities.