Issue 9, 2012

Rotational barriers of biphenyls having heavy heteroatoms as ortho-substituents: experimental and theoretical determination of steric effects

Abstract

The free energies of activation for the aryl–aryl rotation of 17 biphenyl derivatives, bearing a heavy heteroatom (S, Se, Te, P, Si, Sn) as ortho substituent, have been measured by variable temperature NMR. These numbers, so called B values, represent a meaningful measure of the steric hindrance exerted by the selected substituents. DFT computations match quite satisfactorily the experimental barriers and the ground state geometries as well (determined, in two cases, by X-ray diffraction). The present values extend the available list of B values and thus provide an enlarged basis for the compilation of the space requirements of standard substituents, based solely on experimental determinations.

Graphical abstract: Rotational barriers of biphenyls having heavy heteroatoms as ortho-substituents: experimental and theoretical determination of steric effects

Supplementary files

Article information

Article type
Paper
Submitted
05 Oct 2011
Accepted
14 Nov 2011
First published
16 Nov 2011

Org. Biomol. Chem., 2012,10, 1847-1855

Rotational barriers of biphenyls having heavy heteroatoms as ortho-substituents: experimental and theoretical determination of steric effects

L. Lunazzi, M. Mancinelli, A. Mazzanti, S. Lepri, R. Ruzziconi and M. Schlosser, Org. Biomol. Chem., 2012, 10, 1847 DOI: 10.1039/C1OB06688A

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