Kannengießer Raphaela, Lach Marcel J, Stahl Wolfgang, Nguyen Ha Vinh Lam
Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen (Germany).
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).
Chemphyschem. 2015 Jun 22;16(9):1906-11. doi: 10.1002/cphc.201500087. Epub 2015 Apr 27.
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.
利用分子束傅里叶变换微波光谱和量子化学计算相结合的方法，高精度地确定了描述N-乙基乙酰胺乙酰甲基扭转的气相结构和参数。在MP2理论水平上的构象研究在能量面上产生了四个极小值。确定了能量上最有利的具有C1对称性的构象异构体。由于乙酰甲基的扭转势垒为73.4782(1) cm(-1)，在光谱中发现了高达4.9 GHz的精细分裂。构象结构不仅通过转动常数得到证实，还通过内转子的取向得到证实。分析了(14)N四极超精细分裂，并将推导的耦合常数与计算值进行了比较。
