Hannover 2013 – scientific programme

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A: Fachverband Atomphysik

A 23: Dissertation Prize Symposium

A 23.2: Invited Talk

Wednesday, March 20, 2013, 11:30–12:00, E 415

Comparative Studies on some Blackcurrant Odorants and Fruit Esters using a Combination of Microwave Spectroscopy and Quantum Chemical Calculations — •Halima Mouhib — IPC, RWTH Aachen University, Aachen, Germany

Using a combination of molecular beam Fourier transform microwave spectroscopy (MB-FTMW) and different quantum chemical calculations, highly accurate structural information on the lowest energy conformers of molecules can be obtained. This kind of information is especially needed, when a large number of conformations make it difficult to decide which is the lowest in energy.

During the first part of my PhD thesis, I investigated the structures of valerianic ethyl ester (ethyl isovalerate) and its structural isomers ethyl pivalate, ethyl valerate, and 2-methyl ethyl butyrate. The investigated fruit esters turned out to possess large amplitude motions, causing difficulties for the prediction of the theoretical geometries at different levels of theory. The correct geometries could therefore not be predicted properly using calculations at the MP2/6-311++G(d,p) level. Here, the experimental data were crucial to validate the results obtained from quantum chemical calculations and yielded new insight into the structure and dynamics of these small esters. In the second part, the same technique was applied to investigate different types of blackcurrant odorants. Although microwave spectroscopy has recently moved towards solving the structures of sizeable molecules, this was the first approach to determine the gas phase structure of odorants and show the usefulness of this method for structure-odor correlations.