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Conformational isomerism of a-ketoesters: A FTIR and ab initio study

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Ferri, Davide
Baiker, Alfons
Published in Perkin Transactions 2. 2000, vol. 2, p. 221-227
Abstract 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.
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FERRI, Davide, BUERGI, Thomas, BAIKER, Alfons. Conformational isomerism of a-ketoesters: A FTIR and ab initio study. In: Perkin Transactions 2, 2000, vol. 2, p. 221-227. https://archive-ouverte.unige.ch/unige:14653

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Deposited on : 2011-03-18

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