title: Identifying enantiomers in mixtures of chiral molecules with broadband microwave spectroscopy.
abstract: Chirality-sensitive broadband microwave spectroscopy was performed on mixtures of carvone enantiomers and conformers to distinguish enantiomers, measure enantiomeric excesses, and determine the absolute configurations of the enantiomers. This method uses microwave three-wave mixing and is inherently well-suited to the analysis of mixtures-a unique advantage over other techniques. In contrast to conventional microwave spectroscopy, the phase of the received signal is also exploited. This phase depends upon the signs of the molecules' dipole-moment components and is used to identify the excess enantiomer. The measured signal amplitude determines the size of the excess. The broadband capabilities of the spectrometer were used to simultaneously excite and measure two conformers of carvone, demonstrating the analysis of a sample with multiple chiral species. Employing quantum chemical calculations and the measured phases, the absolute configurations of the enantiomers are determined.
authors: Max-Planck-Institut für Struktur und Dynamik der Materie, Luruper Chaussee 149, 22761 Hamburg (Germany); Center for Free-Electron Laser Science, Notkestrasse 85, 22607 Hamburg (Germany).
authors: V Alvin
authors: VA
authors: Shubert
authors: David
authors: D
authors: Schmitz
authors: David
authors: D
authors: Patterson
authors: John M
authors: JM
authors: Doyle
authors: Melanie
authors: M
authors: Schnell
mesh_terms: D000081005:Cyclohexane Monoterpenes; D008872:Microwaves; D008968:Molecular Conformation; D039821:Monoterpenes / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000081005:Cyclohexane Monoterpenes; D039821:Monoterpenes; C006923:carvone
keywords: absolute configuration; chiral mixtures; chirality; enantiomer identification; microwave spectroscopy