Search:
Computing and Library Services - delivering an inspiring information environment

The chemical reactivity of penicillins and other b-lactam antibiotics

Proctor, Philip, Gensmantel, Nigel P. and Page, Michael I. (1982) The chemical reactivity of penicillins and other b-lactam antibiotics. Journal of the Chemical Society, Perkin Transactions 2 (9). pp. 1185-1192. ISSN 1472-779X

Metadata only available from this repository.

Abstract

The rates of the acid catalysed hydrolysis of penicillins and cephalosporins are linear in Ho and, unlike other amides, show no rate maximum with increasing acidity. Electron-withdrawing substituents at C-6 in penicillins decrease the rate of hydrolysis with a I of ca.4 and they decrease the rate when attached to the amine leaving group. The acylamido-group at C-6 in penicillins, but not at C-7 in cephalosporins, exhibits neighbouring group participation with a rate enhancement of ca. 103. The absence of penicillenic acid formation from benzylpenicillin in acidic solution is not due to the ionisation of the carboxy-group. These observations are rationalised by a scheme, involving N-protonation and formation of an acylium ion intermediate. The alkaline hydrolysis of penicillins proceeds 102 faster than a -lactam after correction for substituent effects. There is no evidence for substantial inhibition of amide resonance in the bicyclic -lactam antibiotics, little evidence to indicate extra strain in these systems and no evidence that expulsion of the leaving group at C-3 in cephalosporins occurs in the transition state

Item Type: Article
Subjects: Q Science > Q Science (General)
Q Science > QD Chemistry
Schools: School of Applied Sciences
Related URLs:
Depositing User: Sharon Beastall
Date Deposited: 12 Nov 2009 11:20
Last Modified: 12 Nov 2009 11:20
URI: http://eprints.hud.ac.uk/id/eprint/6214

Item control for Repository Staff only:

View Item

University of Huddersfield, Queensgate, Huddersfield, HD1 3DH Copyright and Disclaimer All rights reserved ©