Letter

Nature 446, 526-529 (29 March 2007) | doi:10.1038/nature05653; Received 19 October 2006; Accepted 5 February 2007

Absolute configuration of chirally deuterated neopentane

J. Haesler1, I. Schindelholz1, E. Riguet1, C. G. Bochet1 & W. Hug1

  1. Department of Chemistry, University of Fribourg, ch. du Musée 9, CH-1700 Fribourg, Switzerland

Correspondence to: J. Haesler1W. Hug1 Correspondence and requests for materials should be addressed to W.H. (Email: w.hug@gmx.net) or J.H. (Email: jacques.haesler@unifr.ch).

The relationship between macroscopic chirality and chirality on the molecular level was unequivocally established in 1951 through anomalous X-ray scattering1. Although this technique became the definitive method for determining the absolute configuration of a molecule, one important limitation of the approach is that the molecule must contain 'heavy' atoms (for example, bromine). The direct determination of absolute configurations for a wider range of molecules has recently become possible by measuring a molecule's vibrational optical activity2, 3. Here we show that instrumental advances in Raman optical activity4, 5, combined with quantum chemical computations6, 7, 8, make it possible to determine the absolute configuration of (R)-[2H12H22H3]-neopentane9. This saturated hydrocarbon represents the archetype of all molecules that are chiral as a result of a dissymmetric mass distribution. It is chemically inert and cannot be derivatized to yield molecules that would reveal the absolute configuration of the parent compound. Diastereomeric interactions with other molecules, optical rotation, and electronic circular dichroism are, in contrast to the well-known case of bromochlorofluoromethane10, 11, 12, not expected to be measurable. Vibronic effects in the vacuum ultraviolet circular dichroism might reveal that the molecule is chiral, but the presence of nine rotamers would make it extremely difficult to interpret the spectra, because the spatial arrangement of the rotamers' nuclei resembles that of enantiomers. The unequivocal spectroscopic determination of the absolute configuration of (R)-[2H12H22H3]-neopentane therefore presented a major challenge, one that was at the very limit of what is possible.

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