Proximity effect on the general base catalysed hydrolysis of amide linkage: the role of cationic surfactant, CTABr

Dash, Sarat C. ; Dash, Anadi C. (2011) Proximity effect on the general base catalysed hydrolysis of amide linkage: the role of cationic surfactant, CTABr Proceedings of the Indian Academy of Sciences - Chemical Sciences, 123 (4). pp. 497-507. ISSN 0253-4134

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Official URL: http://www.ias.ac.in/chemsci/Pdf-Jul2011/497.pdf

Related URL: http://dx.doi.org/10.1007/s12039-011-0084-5

Abstract

The bis phenoxide forms of (1,2)bis(2-hydroxybenzamido)ethane(I), (1,5)bis(2-hydroxybenzamido) 3-azapentane(II), (1,3)bis(2-hydroxybenzamido)propane(III), and (1,8)bis(2-hydroxybenzamido)3,6- diazaoctane(IV) undergo facile hydrolysis of one of the amide groups (0.02 ≤ [OH]T (mol dm−3) ≤ 0.5, 10% MeOH (v/v) + H2O medium) without exhibiting [OH] dependence. The reactivity trend follows I ~ II > > III ~ IV with low activation enthalpy {25.7±2.8 ≤ ΔH≠(kJ mol−1) ≤ 64.8 ± 7.0}. The high negative and comparable values of activation entropy{−234 ± 8 ≤ ΔSΔ (J K−1 mol−1) ≤ −127 ± 20} are consistent with closely similar, and ordered transition states which can be assembled by favourably oriented phenoxide groups. The solvent kinetic isotope effect for I, kH2O/kD2O+H2O ~ 1 (20 and 50 volume% D2O), indicates that proton transfer is not involved as a part of the rate controlling process. The observed slowing down of the rate of this reaction for I in the micellar pseudo phase of CTABr also supports the proposed mechanism. Under premicellar conditions, however, rate acceleration is observed, a consequence believed to be associated with the capping effect of the hydrophobic tail of the surfactant cation forming the reactive ion-pair, CTA+, (I-2H)2− exclusively in the aqueous pseudo phase.

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:2-Hydroxybenzamides; Kinetics; Micellar Effect
ID Code:78333
Deposited On:19 Jan 2012 06:29
Last Modified:18 May 2016 21:11

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