Ethyl valerate, C4H9–COO–C2H5, sometimes called “green apple flavor”, is an important fruit ester with various applications in the food and cosmetic industry. H. Mouhib and W. Stahl, RWTH Aachen University, Germany, report on the gas-phase structures of green apple flavor observed by molecular beam Fourier transform microwave (MB-FTMW) spectroscopy assigned by quantum chemical calculations to obtain accurate conformational data on the two lowest energy conformers.
This method is interesting for future structure–odour studies to determine the lowest energy conformations of odorants and flavors. Especially in cases where numerous conformers exist and small energy differences make it difficult to determine the structure of the lowest energy conformer by quantum chemical calculations alone.
Two different conformers of ethyl valerate were observed in the supersonic jet. One of Cs symmetry and one of C1 symmetry, the latter being the most abundant conformer.
- Conformational Analysis of Green Apple Flavour: The Gas-Phase Structure of Ethyl Valerate Validated by Microwave Spectroscopy,
H. Mouhib, W. Stahl,
ChemPhysChem 2012, 13, 1297–1301.