Imperial College London
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Professor Tom Welton

Faculty of Natural Sciences, Department of Chemistry

Professor of Sustainable Chemistry
 
 
 
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Contact

 

+44 (0)20 7594 5763t.welton Website

 
 
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Location

 

601AMolecular Sciences Research HubWhite City Campus

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Summary

 

Publications

Citation

BibTex format

@article{Smith:2024:10.1039/d4cp00156g,
author = {Smith, GJ and Koutsoukos, S and Lancaster, B and Becker, J and Welton, T and Hunt, PA},
doi = {10.1039/d4cp00156g},
journal = {Phys Chem Chem Phys},
pages = {12453--12466},
title = {Unravelling ionic liquid solvent effects for a non-polar Cope rearrangement reaction.},
url = {http://dx.doi.org/10.1039/d4cp00156g},
volume = {26},
year = {2024}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - The impact of ionic liquids (ILs) on polar reactions is well recognised, however the impact of ILs on non-polar reactions is less well understood or explored. Pericyclic Cope rearrangements are highly concerted, exhibit minimal charge localisation and pass through an uncharged but well-defined transition state, and thus provide a good mechanism for exploring the impact of IL polarizability on chemical reactivity. Recently, a 10× rate enhancement has been observed for the Cope rearrangement of 3-phenyl-1,5-hexadiene in the IL 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C4C1im][NTf2] compared to benzene. In this work we undertake a DFT based computational study (B3LYP-D3BJ/6-311+G(d,p) and M06-2X-D3/6-311+G(d,p)) of the Cope rearrangement of 3-phenyl-1,5-hexadiene and 3-propyl-hexa-1,5-diene in molecular solvents (acetonitrile, benzene and ethanol) and the IL [C4C1im][NTf2] using the SMD solvation model. The impact of benzene and [C4C1im][NTf2] on the Cope rearrangement of 3-phenyl-1,5-hexadiene is studied in more detail and we provide insight into the reason for the rate enhancement in an IL. The volume of activation is evaluated and the potential impact of 'solvent pressure' is discussed. We identify two potential mechanisms for volume effects to contribute to the rate enhancement. Solvent association energies are evaluated at the DLNPO-CCSD(T) level. Specific solvent interactions are explored through atomic partial charge, molecular orbital and bond critical point analysis, as well as via non-colvalent interaction (NCI) plots, electrostatic potential (ESP) differences and density difference Δρ(r) plots. We find that the cation and anion together form an extensive van der Waals pocket in-which the transition state (TS) sits. Electron density within the TS is anisotropically polarised via a 'push-pull' effect due to the dual cation-anion nature of the IL, stabilising the TS relative to benzene. We also provide experimental evidence
AU  - Smith,GJ
AU  - Koutsoukos,S
AU  - Lancaster,B
AU  - Becker,J
AU  - Welton,T
AU  - Hunt,PA
DO  - 10.1039/d4cp00156g
EP  - 12466
PY  - 2024///
SP  - 12453
TI  - Unravelling ionic liquid solvent effects for a non-polar Cope rearrangement reaction.
T2  - Phys Chem Chem Phys
UR  - http://dx.doi.org/10.1039/d4cp00156g
UR  - https://www.ncbi.nlm.nih.gov/pubmed/38625536
VL  - 26
ER  -
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