Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Microwave Spectrum, Barrier to Internal Rotation, and Dipole Moment of Methyl Selenocyanate
Takeshi SakaizumiYoshio KohriOsamu OhashiIchiro Yamaguchi
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1978 Volume 51 Issue 12 Pages 3411-3417


Microwave rotational spectra of five isotopic species of methyl selenocyanate (CH3SeCN with 82Se, 80Se, 78Se, 77Se, and 76Se) in the ground vibrational state, and two isotopic species of methyl selenocyanate-d3 (CD3SeCN with 80Se and 78Se) in the ground and first excited states of the methyl torsional mode have been assigned in the 8.0 to 35.5 GHz frequency range. For the most abundant species in the ground vibrational state, the rotational constants determined are AA=10147±2, BA=3483.57±0.04, and C=2631.58±0.04 MHz for CH380SeCN and A=8322.57±0.81, B=3308.06±0.02, and C=2436.92±0.01 MHz for CD380SeCN. The A-E splittings due to the methyl internal rotation were observed for the rotational transitions in the ground vibrational state for the normal species and in the first excited state of the methyl torsional mode for the deuterated species. Analysis of the splittings gave a barrier height to the methyl internal rotation of 1241±50 and 1228±50 cal/mol for the CH3 and CD3 species, respectively. Stark measurements yielded the principal axis dipole moments of μa=4.35±0.04, μb=0.76±0.10, and the total dipole moment of μ=4.42±0.05 D for CH380SeCN, and μa=4.31±0.04, μb=0.67±0.07, and μ=4.36±0.04 D for CD380SeCN. The direction of the dipole moment in the molecule is discussed.

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