Volume 88, Issue 6 pp. 1375-1386
Research Article

The Effect of Ring Size on Reactivity: The Diagnostic Value of ‘Rate Profiles’

Eric Masson

Eric Masson

Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale, BCH, CH-1015 Lausanne

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Frédéric Leroux

Frédéric Leroux

Laboratoire de Stéréochimie associé au CNRS (UMR CNRS 7509), Université Louis Pasteur (ECPM), 25 rue Becquerel, F-67087 Strasbourg Cedex 2

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First published: 21 June 2005
Citations: 18

Abstract

The rates of cycloalkyl phenyl sulfide formation of a series of homologous bromocycloalkanes upon treatment with sodium benzenethiolate have been determined to ascertain the effect of ring size on reactivity. The ‘rate profile’, i.e., reaction rate vs. ring size, for these nucleophilic substitutions (SN2) was determined. A linear free-energy relationship could be derived from computed hydride affinities of cycloalkanes and rates of typical SN1 reactions, whereas rates of SN2 reactions exhibited a strong discrepancy from the seven- up to the twelve-membered rings. This discrepancy was rationalized by a careful examination of the geometry of the intermediates and transition states involved in these reactions.

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