Issue 27, 2016

SN1 reactions in supercritical carbon dioxide in the presence of alcohols: the role of preferential solvation

Abstract

Ethanol (3b) inhibits SN1 reactions of alkyl halides 1 in supercritical carbon dioxide (scCO2) and gives no ethers as products. The unexpected behaviour of alcohols 3 in the reaction of alkyl halides 1 with 1,3-dimethoxybenzene (2) in scCO2 under different conditions is rationalised in terms of Brønsted and Lewis acid–base equilibria of reagents, intermediates, additives and products in a singular solvent characterised by: (i) the strong quadrupole and Lewis acid character of carbon dioxide, which hinders SN2 paths by strongly solvating basic solutes; (ii) the weak Lewis base character of carbon dioxide, which prevents it from behaving as a proton sink; (iii) the compressible nature of scCO2, which enhances the impact of preferential solvation on carbon dioxide availability for the solvent-demanding rate determining step.

Graphical abstract: SN1 reactions in supercritical carbon dioxide in the presence of alcohols: the role of preferential solvation

Supplementary files

Article information

Article type
Paper
Submitted
19 May 2016
Accepted
07 Jun 2016
First published
07 Jun 2016

Org. Biomol. Chem., 2016,14, 6554-6560

Author version available

SN1 reactions in supercritical carbon dioxide in the presence of alcohols: the role of preferential solvation

T. Delgado-Abad, J. Martínez-Ferrer, R. Acerete, G. Asensio, R. Mello and M. E. González-Núñez, Org. Biomol. Chem., 2016, 14, 6554 DOI: 10.1039/C6OB01097K

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