Acetyl Methyl Torsion in N-Ethylacetamide: A Challenge for Microwave Spectroscopy and Quantum Chemistry.
The gas-phase structures and parameters describing acetyl methyl torsion of N-ethylacetamide are determined with high accuracy, using a combination of molecular beam Fourier-transform microwave spectroscopy and quantum chemical calculations. Conformational studies at the MP2 level of theory yield four minima on the energy surface. The most energetically favorable conformer, which possesses C1 symmetry, is assigned. Due to the torsional barrier of 73.4782(1) cm(-1) of the acetyl methyl group, fine splitting up to 4.9 GHz is found in the spectrum. The conformational structure is not only confirmed by the rotational constants, but also by the orientation of the internal rotor. The (14) N quadrupole hyperfine splittings are analyzed and the deduced coupling constants are compared with the calculated values.
Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen (Germany).
Raphaela
R
Kannengießer
Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen (Germany).
Marcel J
MJ
Lach
Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen (Germany).
Wolfgang
W
Stahl
Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), UMR 7583 (CNRS/Univ. Paris Est & Paris Diderot), Université de Paris Est, 61 avenue du Général de Gaulle, F-94010 Créteil cedex (France). lam.nguyen@lisa.u-pec.fr.
Ha Vinh Lam
HV
Nguyen
D000081:Acetamides / Q000737:chemistry*; D008872:Microwaves; D011789:Quantum Theory
D000081:Acetamides; C047509:N-ethylacetamide
conformational analysis; ethylacetamide; internal rotation; microwave spectroscopy; quadrupole coupling