Structural and spectroscopic characterization of methyl isocyanate, methyl cyanate, methyl fulminate, and acetonitrile N-oxide using highly correlated ab initio methods

被引:17
作者
Dalbouha, S. [1 ,2 ]
Senent, M. L. [1 ]
Komiha, N. [2 ]
Dominguez-Gomez, R. [3 ]
机构
[1] CSIC, Inst Estruct Mat, Dept Quim Fis Teor, Serrano 121, Madrid 28006, Spain
[2] Univ Mohammed 5, Fac Sci Rabat, LS3ME, Equipe Chim Theor & Modelisat, 4 Ave Ibn Battouta BP 1014 RP, Rabat, Morocco
[3] Univ Politecn Madrid, ETS Ingn Civil, Alfonso 12,3-5, Madrid 28014, Spain
关键词
NORMAL-COORDINATE ANALYSIS; MILLIMETER-WAVE SPECTRUM; MICROWAVE-SPECTRUM; DIPOLE-MOMENT; ROTATIONAL SPECTRUM; BASIS-SETS; CH3NCO; METHYLISOTHIOCYANATE; METHYLISOCYANATE; FREQUENCIES;
D O I
10.1063/1.4963186
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Various astrophysical relevant molecules obeying the empirical formula C2H3NO are characterized using explicitly correlated coupled cluster methods (CCSD(T)-F12). Rotational and rovibrational parameters are provided for four isomers: methyl isocyanate (CH3NCO), methyl cyanate (CH3OCN), methyl fulminate (CH3ONC), and acetonitrile N-oxide (CH3CNO). A CH3CON transition state is inspected. A variational procedure is employed to explore the far infrared region because some species present non-rigidity. Second order perturbation theory is used for the determination of anharmonic frequencies, rovibrational constants, and to predict Fermi resonances. Three species, methyl cyanate, methyl fulminate, and CH3CON, show a unique methyl torsion hindered by energy barriers. In methyl isocyanate, the methyl group barrier is so low that the internal top can be considered a free rotor. On the other hand, acetonitrile N-oxide presents a linear skeleton, C-3v symmetry, and free internal rotation. Its equilibrium geometry depends strongly on electron correlation. The remaining isomers present a bend skeleton. Divergences between theoretical rotational constants and previous parameters fitted from observed lines for methyl isocyanate are discussed on the basis of the relevant rovibrational interaction and the quasi-linearity of the molecular skeleton. Published by AIP Publishing.
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页数:10
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