Effective charge development in the transfer of the acetyl group between nucleophiles in acetonitrile solution: Acetolysis and butylaminolysis of substituted phenyl esters

Maude, Antony B. and Williams, Andrew (1997) Effective charge development in the transfer of the acetyl group between nucleophiles in acetonitrile solution: Acetolysis and butylaminolysis of substituted phenyl esters. Journal of the Chemical Society-Perkin Transactions 2 (2). pp. 179-183. ISSN 0300-9580. (The full text of this publication is not available from this repository)

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Abstract

Equilibrium and rate constants have been measured for the phenolyses of acetic anhydride in acetonitrile solution, Acetolysis of substituted phenyl acetates by acetate ion possesses a Bronsted beta(lg) value of -1.50 which, together with a beta(eq) value of 2.86, indicates substantial fission of the C-OAr bond in the transition structure, The value of beta(eq) is employed to identify the rate-limiting steps in aminolyses in acetonitrile. Butylaminolysis of substituted phenyl acetates in acetonitrile solution yields amide and substituted phenolate anion and the kinetics obey the general rate law: Rate = k(1)[ester][amine] + k(2)[ester][amine](2) + k(3)[ester][amine][18-crown-6] Free energy plots of log k(1) and log k(2) exhibit breaks near pK(a)(ArOH) values of 9 and 8, respectively, and these can be interpreted by a mechanism which involves a common zwitterionic adduct T-+/-, which partitions to give the product by two routes: A involving direct expulsion of the phenolate ion leaving group (k(1) parameter) and B involving proton transfer prior to phenolate ion expulsion (k(2) parameter). The formation of T-+/- is rate-limiting for the A path and C-OAr bond fission is rate-limiting for the B mechanism.

Item Type: Article
Subjects: Q Science
Q Science > QD Chemistry
Divisions: Faculties > Science Technology and Medical Studies > School of Physical Sciences
Depositing User: M.A. Ziai
Date Deposited: 19 Apr 2009 19:36
Last Modified: 25 Jun 2014 13:20
Resource URI: http://kar.kent.ac.uk/id/eprint/18178 (The current URI for this page, for reference purposes)
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