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Complexation catalysis: effective charge development in the aminolysis of phenyl esters in chlorobenzene catalysed by crown ethers

Maude, Antony B., Williams, Andrew (1995) Complexation catalysis: effective charge development in the aminolysis of phenyl esters in chlorobenzene catalysed by crown ethers. Journal of the Chemical Society-Perkin Transactions 2, (4). pp. 691-696. ISSN 0300-9580. (doi:10.1039/P29950000691) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided) (KAR id:19370)

The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided.
Official URL:
http://dx.doi.org/10.1039/P29950000691

Abstract

Kinetics of the butylaminolysis of substituted phenyl acetates in chlorobenzene in the presence of a variety of crown ethers obey the following rate law. Rate = k(b)[BuNH(2)](2)[Ester] + k(c)[BuNH(2)][Crown][Ester] The individual rate constants fit Bronsted-type relationships: log k(b) = -0.75 pK(a) + 4.21 log k(c) = -0.58 pK(a) + 3.41 [18-crown-6] log k(c) = -0.61 pK(a) + 3.18 [12-crown-4] where pK(a) refers to the ionization of the phenol in aqueous solution. The Bronsted beta(1g) values for k(b) and k(c) are calibrated with the value of beta(eq) recently determined for acetyl transfer between phenolate ions in chlorobenzene. The sensitivity, beta(1g), of k(c) is consistent with the rate-limiting formation of a crown ether-zwitterion adduct with subsequent fast (non-rate-limiting) ArO-C bond fission. The Bronsted data for k(b) when calibrated by beta(eq) is consistent with rate-limiting proton transfer from zwitterion to base. 18-Crown-6 enables proton transfer to occur between phenol and butylamine in chlorobenzene according to the equation: BuNH(2) + ArOH + Crown reversible arrow Bu-NH3+. Crown + ArO- equilibrium constant (K) for the above reaction with a series of substituted phenols has a Bronsted selectivity (beta) of 2.1 compared with that for the ionization of phenols in water.

Item Type: Article
DOI/Identification number: 10.1039/P29950000691
Subjects: Q Science > QD Chemistry
Divisions: Divisions > Division of Natural Sciences > Biosciences
Depositing User: O.O. Odanye
Date Deposited: 04 Jun 2009 10:48 UTC
Last Modified: 16 Nov 2021 09:57 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/19370 (The current URI for this page, for reference purposes)

University of Kent Author Information

Williams, Andrew.

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