%0 Journal Article %A Ferri, Davide %A Bürgi, Thomas %A Baiker, Alfons %T Conformational isomerism of a-ketoesters: A FTIR and ab initio study %J Journal of the Chemical Society. Perkin transactions 2 %@ 0300-9580 %V 2 %P 221-227 %D 2000 %R 10.1039/a908466e %U http://dx.doi.org/10.1039/a908466e %U http://archive-ouverte.unige.ch/unige:14653 %X The conformational behaviour of several α-ketoesters was investigated using solution FTIR in combination with ab initio calculations. The α-ketoesters show marked differences in the O=C–C=O torsional potential energy surface depending on the substituent at the α-keto group. In general the torsional potential is characterised by broad minima corresponding to s-cis and s-trans conformations and low interconversion barriers. The s-trans conformation is more stable but the fraction of s-cis is considerable at room temperature and increases with solvent polarity due to the higher dipole moment of the latter. Hydrogen bonding with alcoholic solvents also leads to a stabilisation of the s-cis conformer. The interaction of ethyl pyruvate with R3N+–H is much stronger when ethyl pyruvate adopts an s-cis conformation due to strong ion–dipole interaction. This type of interaction between ethyl pyruvate and protonated cinchonidine is considered to be crucial for the enantio-differentiation in the heterogeneous enantioselective hydrogenation of ethyl pyruvate over cinchonidine modified platinum in acidic media.