VIBRATIONAL OPTICAL-ACTIVITY OF (S)-1-D-ETHANOL

Ethanol and (S)-I-d-ethanol have been investigated by ab initio molecular orbital calculations and by experimental measurements of IR and VCD spectra. The structures and relative energies of the anti and gauche conformers have been determined, including corrections for zero-point vibrational energy. Ethanol exists as 42:58 mixture of anti-.gauche forms. The gauche rotamers are inherently chiral structures, and their VCD spectra have been determined by ab initio application of vibronic coupling theory. Deuterium substitution of the pro-S hydrogen atom results in a slight preference for the M rotamer over the P form because of the lower zero-point vibrational energy of the former. The IR spectrum of ethanol and the IR and VCD spectra of (S)-I-d-ethanol have been determined theoretically by application of the vibronic coupling formalism of Nafie and Freedman, and the experimental VCD spectrum of (S)-I-d-ethanol has been measured in the 800-1350-cm-1 range. Some features of the spectrum may be attributed to the absolute configuration at the asymmetric carbon atom, independent of conformation, while others are associated with the chirality of the gauche forms of the compound. © 1990, American Chemical Society. All rights reserved.