| Institution: | 1. Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany
Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS UMR Université Paris-Est Créteil, Université de Paris, Institute Pierre Simon Laplace, 61 avenue du Général de Gaulle, 94010 Créteil, France;2. Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany;3. Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS UMR Université Paris-Est Créteil, Université de Paris, Institute Pierre Simon Laplace, 61 avenue du Général de Gaulle, 94010 Créteil, France |
| Abstract: | Methyl n-alkyl ketones form a class of molecules with interesting internal dynamics in the gas-phase. They contain two methyl groups undergoing internal rotations, the acetyl methyl group and the methyl group at the end of the alkyl chain. The torsional barrier of the acetyl methyl group is of special importance, since it allows for the discrimination of the conformational structures. As part of the series, the microwave spectrum of octan-2-one was recorded in the frequency range from 2 to 40 GHz, revealing two conformers, one with C1 and one with Cs symmetry. The barriers to internal rotation of the acetyl methyl group were determined to be 233.340(28) cm?1 and 185.3490(81) cm?1, respectively, confirming the link between conformations and barrier heights already established for other methyl alkyl ketones. Extensive comparisons to molecules in the literature were carried out, and a small overview of general trends and rules concerning the acetyl methyl torsion is given. For the hexyl methyl group, the barrier height is 973.17(60) cm?1 for the C1 conformer and 979.62(69) cm?1 for the Cs conformer. |
