Absolute configuration of chirally deuterated neopentane

• Published in: Nature Vol. 446; no. 7135; pp. 526 - 529
• Main Authors: Schindelholz, I, Hug, W, Haesler, J, Riguet, E, Bochet, C. G
• Format: Journal Article
• Language: English
• Published: LONDON Springer Nature 29.03.2007; Nature Publishing; Nature Publishing Group
• Subjects: Atomic and molecular physics; Bromine; Chemistry; Chirality; Deuteration; Dichroism; Electronics; Exact sciences and technology; General molecular conformation and symmetry; stereochemistry; Hydrocarbons; Molecular properties and interactions with photons; Molecular spectra; Molecular structure; Multidisciplinary Sciences; Neopentane; Optical activity; Optical activity and dichroism; magnetooptical and electrooptical spectra; Optics; Physics; Properties of molecules and molecular ions; Quantum chemistry; Raman and rayleigh spectra (including optical scattering); Saturated hydrocarbons; Science & Technology; Science & Technology - Other Topics; Ultraviolet; X-rays; RAMAN OPTICAL-ACTIVITY; HYDROGEN; MODES; CIRCULAR-DICHROISM; BROMOCHLOROFLUOROMETHANE; ISOTOPIC-SUBSTITUTION; INTERNAL ROTATION; SCATTERING; MOLECULES; Raman spectra; Absolute configuration; Optical activity; Hydrocarbons; Chiral compound; Isotopic species; NMR spectra; Deuterium Compounds; Organic compounds; Neopentane
• ISSN: 0028-0836; 1476-4687; 1476-4679
• DOI: 10.1038/nature05653

The relationship between macroscopic chirality and chirality on the molecular level was unequivocally established in 1951 through anomalous X-ray scattering. 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 activity. Here we show that instrumental advances in Raman optical activity, combined with quantum chemical computations, make it possible to determine the absolute configuration of (R)-[2H1, 2H2, 2H3]-neopentane. 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 bromochlorofluoromethane, 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)-[2H1, 2H2, 2H3]-neopentane therefore presented a major challenge, one that was at the very limit of what is possible.