Reactions within association complexes: acid catalysed hydrolysis of substituted benzaldehyde acetals in the presence of detergents

Rose, Philip D. R. and Williams, Andrew (2002) Reactions within association complexes: acid catalysed hydrolysis of substituted benzaldehyde acetals in the presence of detergents. Journal of the Chemical Society-Perkin Transactions 2 (9). pp. 1589-1595. ISSN 1472-779X. (The full text of this publication is not available from this repository)

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Abstract

First order rate constants for decomposition of substituted benzaldehyde dimethyl acetals at constant pH in solutions of sodium dodecyl sulfate (SDS) and Aerosol AOT (AOT) maintained at constant [Na+] are linear in surfactant concentration. When the only Na+ is that derived from the added SDS the kinetics exhibit a saturating rate law in SDS concentration. The present study shows that the curvature is not due to complexation of substrate but to ion exchange whereby increasing [Na+] expels H+ from the Stern region where reaction of the substrate occurs. Increasing [Na+] at constant [SDS] inhibits the SDS-catalysed acid hydrolysis of 4-isopropylbenzaldehyde dimethyl acetal and the dissociation constant of the Na+-SDS micelle complex is 0.0281 M which agrees with values calculated from previous data using different reactions. The complex to SDS of a neutral analogue of the acetals exhibits a dissociation constant (K-i) which is not significantly dependent on the overall concentration of Na+ ions in the range 0.07 to 0.42 M. Increasing concentrations of cetyltrimethylammonium bromide (CTAB; cetyl = hexadecyl) inhibit the acid catalysed hydrolysis; equilibrium constants (Ki) for the dissociation of the CTAB-complexed acetals fit a Hansch plot and possess no contribution from Hammett's sigma.

Item Type: Article
Additional information: 25 ROYAL SOC CHEMISTRY 587ZQ
Uncontrolled keywords: AQUEOUS-SOLUTION; RESONANCE; INTERMEDIATE; SEPARATION; CONSTANTS; POLAR; ION
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Physical Sciences
Depositing User: Maggie Francis
Date Deposited: 21 Oct 2008 17:04
Last Modified: 25 Jun 2014 13:19
Resource URI: http://kar.kent.ac.uk/id/eprint/11015 (The current URI for this page, for reference purposes)
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