The r0 structural parameters, vibrational spectra, ab initio calculations and barriers to internal rotation and linearity of methylisocyanate

Zhou, Sarah Xiaohua; Durig, J. R.

doi:10.1016/j.molstruc.2008.12.011

Cited by 12 publications

(11 citation statements)

References 30 publications

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“…It is not new that MIC is amongst the molecules exhibiting a strong resonance between the m CH and 2b CH modes [69]. Moreover, Zhou and Durig have recently reported [35] the positions of all three of the CH 3 stretching modes of MIC to have significant differences in frequencies with the changes of phase (for gaseous, liquid and solid MIC), which does not help in the interpretation of the present matrix-isolation experimental data.…”

Section: Methodsmentioning

confidence: 65%

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Infrared spectra of methyl isocyanate isolated in Ar, Xe and N2 matrices

Reva¹,

Lapiński²,

Fausto³

2010

Journal of Molecular Structure

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The infrared spectra of methyl isocyanate monomer isolated in cryogenic argon, xenon and nitrogen matrices were studied. Interpretation of the experimental results was supported by harmonic and anharmonic calculations carried out at the DFT, MP2 and CCSD levels of approximation. Spectral indicators of the molecule structural flexibility were examined, the most striking of these being the multiplet structure of the most intense infrared band due to the antisymmetric stretching vibration of the N@C@O group. The observed quadruplet, spanning over the frequency range of nearly 100 cm À1 , between 2350 and 2250 cm À1 , was interpreted in terms of coupling with the low frequency torsion of the methyl group.

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Section: Methodsmentioning

confidence: 65%

“…The structure of MIC, barriers to internal rotation as well as the vibrational spectra of this compound have been the subject of several computational studies [30][31][32][33][34]. Experimental infrared and Raman spectra of gaseous, liquid and solid MIC were also reported [34,35].…”

Section: Introductionmentioning

confidence: 99%

Infrared spectra of methyl isocyanate isolated in Ar, Xe and N2 matrices

Reva¹,

Lapiński²,

Fausto³

2010

Journal of Molecular Structure

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“…Electron diffraction (Eyster et al 1940; Anderson et al 1972), microwave (MW) spectra (Curl et al 1963; Lett & Flygare 1967; Koput 1984; Koput 1986; Kasten et al 1986) and theoretical calculations (Koput 1988; Sullivan et al 1994; Zhou & Durig 2009; Reva et al 2010, Dalbouha et al 2016) indicate that the CH 3 NCO molecule is an asymmetric top with a CNC angle of about 140° and a small barrier (≈ 20-30 cm -1 ) for the torsion of the methyl group. Its large amplitude internal motions (CH 3 torsion and CNC bend) complicate the spectral analysis and although the high accuracy of the available experimental data (Cernicharo et al 2016) has allowed the detection of this molecule in the gas phase of the ISM, an appreciable discrepancy persists in the value of the A rotational constant (Halfen et al 2015; Cernicharo et al 2016; Dalbohua et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Laboratory study of methyl isocyanate ices under astrophysical conditions

Maté

Molpeceres

Timón

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Methyl isocyanate has been recently detected in comet 67P/ Churyumov-Gerasimenko (67P/CG) and in the interstellar medium. New physicochemical studies on this species are now necessary as tools for subsequent studies in astrophysics. In this work, infrared spectra of solid CHNCO have been obtained at temperatures of relevance for astronomical environments. The spectra are dominated by a strong, characteristic multiplet feature at 2350-2250 cm, which can be attributed to the antisymmetric stretching of the NCO group. A phase transition from amorphous to crystalline methyl isocyanate is observed at ~ 90 K. The band strengths for the absorptions of CHNCO in ice at 20 K have been measured. Deuterated methyl isocyanate is used to help with the spectral assignment. No X-ray structure has been reported for crystalline CHNCO. Here we advance a tentative theoretical structure, based on Density Functional Theory (DFT) calculations, derived taking as a starting point the crystal of isocyanic acid. A harmonic theoretical spectrum is calculated then for the proposed structure, and compared with the experimental data. A mixed ice of HO and CHNCO was formed by simultaneous deposition of water and methyl isocyanate at 20 K. The absence of new spectral features indicates that methyl isocyanate and water do not react appreciably at 20 K, but form a stable mixture. The high CHNCO/HO ratio reported for comet 67P/CG, and the characteristic structure of the 2350-2250 cm band, make of it a very good candidate for future astronomical searches.

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“…The substitution of the pseudohalogen NCO and NCS to a hydrocarbon (R) results in a very large CNC(X) angle, [1,2] which may result in a very low wavenumber CNC bend with only a few bound vibrational states with the remaining molecules having essentially free internal rotation, which has been found for CH 3 NCO 1 and CH 3 NCS 2 . However, when these pseudohalogens are substituted on a silane, the question arises whether there is more than one bound state for the SiNC(X) bend or simply a small 'hump' in the potential function governing the SiNC bending mode as the effective structure is a linear heavy atom skeleton.…”

Section: Introductionmentioning

confidence: 86%

Raman and infrared spectra, conformational stability, ab initio calculations and vibrational assignment of dimethylsilylisocyanate

Guirgis

Zhou

Durig

2009

J Raman Spectroscopy

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The Raman (3200-30 cm −1 ) and/or infrared spectra (3500 to 400 cm −1 ) of gaseous, liquid and solid dimethylsilylisocyanate, (CH 3 ) 2 Si(H)NCO, have been recorded. The MP2(full) calculations, employing a variety of basis sets with and without diffusion functions, have been used to predict the structural parameters, conformational stability, vibrational fundamental wavenumbers, Raman activities, depolarization values and infrared intensities to support the vibrational assignment. The low wavenumber Raman spectrum of the gas with a significant number of Q-branches for the SiNC(O) bend is consistent with an essentially linear SiNCO moiety. The ab initio calculations supported this conclusion as all possible orientations of the NCO moiety lead to nearly the same energy. This result is at variance with the conclusion from the electron diffraction study that the heavy atom skeleton was bent with an angle of 152(5) • with one stable cis conformer. It is believed that this reported angle difference from 180 • is due to the shrinkage effect. The SiH distance of 1.486 Å has been obtained from the isolated SiH stretching wavenumber. From the adjustment of the ab initio MP2(full)/6-311+G(d,p) predicted structural parameters, a proposed structure is reported, which is expected to give rotational constants within a few megahertz of the actual ones. These experimental and theoretical results are compared with the corresponding quantities of similar molecules.

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The r0 structural parameters, vibrational spectra, ab initio calculations and barriers to internal rotation and linearity of methylisocyanate

Cited by 12 publications

References 30 publications

Infrared spectra of methyl isocyanate isolated in Ar, Xe and N2 matrices

Infrared spectra of methyl isocyanate isolated in Ar, Xe and N2 matrices

Laboratory study of methyl isocyanate ices under astrophysical conditions

Raman and infrared spectra, conformational stability, ab initio calculations and vibrational assignment of dimethylsilylisocyanate

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