Ionic liquid effects on a multistep process. Increased product formation due to enhancement of all steps

Sinead T. Keaveney, Ronald S. Haines, Jason B. Harper

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)
7 Downloads (Pure)

Abstract

The reaction of a series of substituted benzaldehydes with hexylamine was examined in acetonitrile and an ionic liquid. In acetonitrile, as the electron withdrawing nature of the substituent increases, the overall addition-elimination process becomes faster as does the build-up of the aminol intermediate. Under equivalent conditions in an ionic liquid, less intermediate build up is observed, and the effect on the rate on varying the substituent is different to that in acetonitrile. Extensive kinetic analysis shows that the ionic liquid solvent increases the rate constant of all steps of the reaction, resulting in faster product formation relative to acetonitrile; these effects increase with the proportion of ionic liquid in the reaction mixture. Differences in the equilibrium position of the addition step in the ionic liquid were found to account for both the decrease in intermediate build up relative to acetonitrile, as well as the differing trend in the overall rate of product formation as the substituent was changed. The microscopic origins of these ionic liquid effects were probed through temperature dependent analyses, highlighting the subtle balance of interactions between the ionic liquid and species along the reaction coordinate, particularly the importance of charge development in the transition state.
Original languageEnglish
Pages (from-to)8925-8936
Number of pages12
JournalOrganic and Biomolecular Chemistry
Volume13
Issue number33
DOIs
Publication statusPublished - 7 Sep 2015
Externally publishedYes

Bibliographical note

Copyright the Publisher 2015. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

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