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

Ian Williams, Philippe Wilson

Research output: Contribution to journalArticle

2 Citations (Scopus)
28 Downloads (Pure)

Abstract

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.
Original languageEnglish
Pages (from-to)7235-7240
Number of pages6
JournalOrganic and Biomolecular Chemistry
Volume15
Issue number34
Early online date18 Aug 2017
DOIs
Publication statusPublished - 14 Sep 2017

Fingerprint

Lactones
closures
continuums
rings
Gibbs free energy
isotope effect
water
Water
enthalpy
Energy barriers
free energy
Succinic Acid
activation
substitutes
electrostatics
Vacuum
Static Electricity
Isotopes
vacuum
Free energy

Cite this

A computational study of the influence of methyl substituents on competitive ring closure to α- and β-lactones. / Williams, Ian; Wilson, Philippe.

In: Organic and Biomolecular Chemistry, Vol. 15, No. 34, 14.09.2017, p. 7235-7240.

Research output: Contribution to journalArticle

@article{19fc84e0774249bcb1f5d3feef0c91c3,
title = "A computational study of the influence of methyl substituents on competitive ring closure to α- and β-lactones",
abstract = "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.",
author = "Ian Williams and Philippe Wilson",
year = "2017",
month = "9",
day = "14",
doi = "10.1039/C7OB01653K",
language = "English",
volume = "15",
pages = "7235--7240",
journal = "Organic and Biomolecular Chemistry",
issn = "1477-0520",
publisher = "Royal Society of Chemistry",
number = "34",

}

TY - JOUR

T1 - A computational study of the influence of methyl substituents on competitive ring closure to α- and β-lactones

AU - Williams, Ian

AU - Wilson, Philippe

PY - 2017/9/14

Y1 - 2017/9/14

N2 - 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.

AB - 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.

U2 - 10.1039/C7OB01653K

DO - 10.1039/C7OB01653K

M3 - Article

VL - 15

SP - 7235

EP - 7240

JO - Organic and Biomolecular Chemistry

JF - Organic and Biomolecular Chemistry

SN - 1477-0520

IS - 34

ER -