Maude, A.B. and Williams, A. (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.
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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: | 19 Apr 2009 19:36 |
| Resource URI: | http://kar.kent.ac.uk/id/eprint/18178 (The current URI for this page, for reference purposes) |
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