Issue 1, 2017

Sizing the role of London dispersion in the dissociation of all-meta tert-butyl hexaphenylethane

Abstract

The structure and dynamics of enigmatic hexa(3,5-di-tert-butylphenyl)ethane was characterized via NMR spectroscopy for the first time. Our variable temperature NMR analysis demonstrates an enthalpy–entropy compensation that results in a vanishingly low dissociation energy (ΔG298d = −1.60(6) kcal mol−1). An in silico study of increasingly larger all-meta alkyl substituted hexaphenylethane derivatives (Me, iPr, tBu, Cy, 1-Ad) reveals a non-intuitive correlation between increased dimer stability with increasing steric crowding. This stabilization originates from London dispersion as expressed through the increasing polarizability of the alkyl substituents. Substitution with conformationally flexible hydrocarbon moieties, e.g., cyclohexyl, introduces large unfavourable entropy contributions. Therefore, using rigid alkyl groups like tert-butyl or adamantyl as dispersion energy donors (DED) is essential to help stabilize extraordinary bonding situations.

Graphical abstract: Sizing the role of London dispersion in the dissociation of all-meta tert-butyl hexaphenylethane

Supplementary files

Article information

Article type
Edge Article
Submitted
21 Jun 2016
Accepted
22 Aug 2016
First published
23 Aug 2016
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2017,8, 405-410

Sizing the role of London dispersion in the dissociation of all-meta tert-butyl hexaphenylethane

S. Rösel, C. Balestrieri and P. R. Schreiner, Chem. Sci., 2017, 8, 405 DOI: 10.1039/C6SC02727J

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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