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A single aqueous reference equilibrium constant for amide synthesis-hydrolysis

Ulijn, R.V. and Moore, B.D. and Janssen, A.E.M. and Halling, P.J. (2002) A single aqueous reference equilibrium constant for amide synthesis-hydrolysis. Journal of the Chemical Society, Perkin Transactions 2, 2002 (5). pp. 1024-1028. ISSN 1472-779X

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Abstract

Experimentally measured equilibrium constants at a given pH in part reflect the contributions of ionisation of acidic and basic groups present. These contributions can be isolated from the equilibrium constant by expressing all reactant concentrations in terms of the uncharged forms only. This article presents methods to calculate uncharged reference equilibrium constants for amide synthesis/hydrolysis reactions. For zwitterions in particular these methods are not always straightforward. It is explained how (microscopic) pK(a) values can be estimated where experimental values are not available. A large number of equilibrium data are analysed for hydrolysis or synthesis of protected and unprotected di- and tri-peptides, beta-lactam antibiotics, and acyl acids and amides. This reveals just how similar the reference equilibrium constants are when ionisation is properly accounted for (K-ref(0) = 10(3.6) M-1) regardless of the molecular form of the reactants involved.

Item type: Article
ID code: 327
Keywords: Thermodynamically controlled synthesis, beta-lactam antibiotics, peptide-synthesis, amoxicillin, thermolysin, protease, systems, salts, Chemistry
Subjects: Science > Chemistry
Department: Faculty of Science > Pure and Applied Chemistry
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Depositing user: Users 16 not found.
Date Deposited: 13 Mar 2006
Last modified: 04 Oct 2012 15:24
URI: http://strathprints.strath.ac.uk/id/eprint/327

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