Hydrogen bonding in homochiral dimers of hydroxyesters studied by Raman optical activity spectroscopy

Spectroscopic analysis of homochiral dimerization is important for the understanding of the homochirality of life and enantioselective catalysis. In this paper, (S)-methyl lactate and related molecules were studied to provide detailed structural information on hydrogen bonding in homochiral dimers of chiral a-hydroxyesters through the experimental and theoretical study of Raman optical activity. Different homochiral dimers can be distinguished by comparing their simulated Raman optical activity spectra with the experimental results. Hydrogen bonding motions are decoded with the aid of vibrational motion analysis, which are apparently involved in vibrational motions below 800?cm1. A common feature related to the chain-bending mode also indicates the absolute configuration of methyl lactate and related molecules. The differing behavior of electric dipoleelectric quadrupole invariants (beta(A)2) compared with the electric dipolemagnetic dipole invariant (beta(G')2), suggests that the intermolecular hydrogen bonding motion behaves differently from the intramolecular one in the asymmetric molecular electric and magnetic fields. These results may help understand hydrogen-bonded self-recognition and other dynamical features in chiral recognition. Copyright (c) 2011 John Wiley & Sons, Ltd.