Dimethyl Sulfide鈥揇imethyl Ether and Ethylene Oxide鈥揈thylene Sulfide Complexes Investigated by Fourier Transform Microwave Spectroscopy and Ab Initio Calculation

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• 作者：Yoshiyuki Kawashima ; Yoshio Tatamitani ; Takayuki Mase Eizi Hirota
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：October 22, 2015
• 年：2015
• 卷：119
• 期：42
• 页码：10602-10612
• 全文大小：410K
• ISSN：1520-5215

文摘

The ground-state rotational spectra of the dimethyl sulfide鈥揹imethyl ether (DMS鈥揇ME) and the ethylene oxide鈥揺thylene sulfide (EO鈥揈S) complexes were observed by Fourier transform microwave spectroscopy, and a-type and c-type transitions were assigned for the normal, ³⁴S, and three ¹³C species of the DMS鈥揇ME and a-type and b-type transitions for the normal, ³⁴S, and two ¹³C species of the EO鈥揈S complexes. The transition frequencies measured for both the complexes were analyzed by using an S-reduced asymmetric-top rotational Hamiltonian. The rotational parameters thus derived for the DMS鈥揇ME were found to be consistent with a structure of C_s symmetry with the DMS bound to the DME by two C鈥揌(DMS)路路路O and one S路路路H鈥揅(DME) hydrogen bonds. Some high-K_a lines were found to be split, and we have interpreted these splittings in terms of internal rotations of the two methyl groups of the DMS and of the 鈥渇ree鈥? i.e., outer group, of the DME. Some forbidden transitions were also observed in cases where K_a = 3 levels were involved, for the DMS鈥揇ME complex in the internal-rotation E state. The barrier height, V₃, to internal rotation of the CH₃ in the DME thus derived is smaller than that of the DME monomer, while the V₃ of the CH₃ groups in the DMS is nearly the same as that of the DMS monomer. For the EO鈥揈S complex, the observed data were interpreted in terms of an antiparallel structure of C_s symmetry with the EO bound to the ES by two C鈥揌(ES)路路路O and two S路路路H鈥揅(EO) hydrogen bonds. An attempt was also made to observe a-type transitions of the DMS dimer without success. We have applied a natural bond orbital analysis to the DMS鈥揇ME and EO鈥揈S to calculate the stabilization energy CT (= 螖E_蟽蟽*), which was correlated closely with the binding energy as found for other related complexes.