Issue 37, 2020

The effect of bisimidazolium-based ionic liquids on a bimolecular substitution process. Are two head(group)s better than one?

Abstract

A homologous series of biscationic ionic liquids based on two imidazolium centres, separated by alkyl chains of varying length, were examined as solvents for a bimolecular substitution reaction across a range of proportions of ionic liquid in the reaction mixture. Their effects on the rate constant of the process were compared to monocationic ionic liquids, with generally a greater rate constant increase observed. Importantly, it was observed that the magnitude of the effect was shown to vary with the length of the linking chain. To investigate the origins of these solvent effects, temperature dependent kinetic studies were performed to obtain activation parameters at high and low mole fractions of ionic liquid. The observed activation parameters showed the rate constant enhancement was due to interaction of the ionic liquid with the starting materials, consistent with previous results. Significantly, however, these data also showed that the balance of enthalpic and entropic effects varied dramatically with the length of the alkyl chain between the cationic centres.

Graphical abstract: The effect of bisimidazolium-based ionic liquids on a bimolecular substitution process. Are two head(group)s better than one?

Supplementary files

Article information

Article type
Paper
Submitted
21 Jūl. 2020
Accepted
04 Sept. 2020
First published
05 Sept. 2020

Org. Biomol. Chem., 2020,18, 7388-7395

The effect of bisimidazolium-based ionic liquids on a bimolecular substitution process. Are two head(group)s better than one?

K. T.-C. Liu, R. S. Haines and J. B. Harper, Org. Biomol. Chem., 2020, 18, 7388 DOI: 10.1039/D0OB01500H

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