A computational study of the influence of methyl substituents on competitive ring closure to α- and β-lactones

Wilson, P.B. ORCID: 0000-0003-0207-2246 and Williams, I.H., 2017. A computational study of the influence of methyl substituents on competitive ring closure to α- and β-lactones. Organic and Biomolecular Chemistry, 15 (34), pp. 7235-7240. ISSN 1477-0520

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Ring-closure of substituted 2-chlorosuccinates to α- or β-lactones has been studied by means of MP2/6-311+G(d,p)//MP2/6-31+G(d) calculations in water treated as a polarised continuum (PCM) and in vacuum. Optimised geometries have been obtained for 2-chlorosuccinate and its 2-methyl, 3,3-dimethyl, and 2,3,3-trimethyl derivatives, along with the transition structures and products for intramolecular nucleophilic displacement leading to the 3- or 4-membered rings. Relative enthalpies and Gibbs free energies of activation and reaction are presented, along with key geometrical parameters, and changes in electrostatic-potential-derived atomic charges. The difference in free-energy barriers for α- and β-lactone formation from the 2-methyl substrate at 298 K is less than 1 kJ mol−1. Primary 14C kinetic isotope effects calculated for substitution at C2 are significantly smaller for α-lactone formation than for β, suggesting a possible way to distinguish between the competing pathways of reaction. The B3LYP method without dispersion corrections predicts the wrong relative stability order for methyl-substituted succinate dianions in PCM water.

Item Type: Journal article
Publication Title: Organic and Biomolecular Chemistry
Creators: Wilson, P.B. and Williams, I.H.
Publisher: Royal Society of Chemistry
Date: 2017
Volume: 15
Number: 34
ISSN: 1477-0520
Rights: This journal is © The Royal Society of Chemistry 2017. Open Access Article. Published on 18 August 2017. Downloaded on 7/15/2020 3:37:35 PM. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Divisions: Schools > School of Animal, Rural and Environmental Sciences
Record created by: Jonathan Gallacher
Date Added: 17 Jun 2020 08:06
Last Modified: 31 May 2021 15:19
URI: https://irep.ntu.ac.uk/id/eprint/40014

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