| Institution: | 1. Laboratoire de Spectroscopie Atomique, Moléculaire et Applications, Département de Physique, Faculté des Sciences de Tunis –, University of Tunis El Manar, 2092 Manar II, Tunis, Tunisia
Université Paris-Est Marne-la-Vallée, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée, France;2. Laboratoire de Spectroscopie Atomique, Moléculaire et Applications, Département de Physique, Faculté des Sciences de Tunis –, University of Tunis El Manar, 2092 Manar II, Tunis, Tunisia;3. RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany;4. Université Paris-Est Marne-la-Vallée, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée, France |
| Abstract: | To accurately characterize the large amplitude motions and soft degrees of freedom of isolated molecules, sampling their conformational landscape by molecular mechanics and quantum chemical calculations may provide a valuable insight into the structure and dynamics. However, the resulting models need to be validated by a reliable experimental counterpart. For ethyl pentanoates, which belong to the family of fruit esters, benchmark calculations at different levels of theory showed that the C−C bond in proximity to the ester carbonyl group exhibits a large amplitude motion that is extremely sensitive to the choice of quantum chemical method and basis set. In such cases, insights from high-resolution molecular jet techniques are ideal to accurately identify and characterize soft degrees of freedom. Here, we report on the most abundant conformer of ethyl 2-ethyl butyrate using Fourier-transform microwave spectroscopy. We show that – unlike other structurally related pentanoates for which gas-phase and crystallographic data is available – ethyl 2-ethyl butyrate possesses a Cs symmetry plane under molecular jet conditions. |
