Analysis of theν3,ν6,ν7+ν8Fermi and Coriolis interacting band system in methyl cyanide

Duncan, J.L.; Ellis, David; Wright, I.J.

doi:10.1080/00268977100100641

Cited by 31 publications

(3 citation statements)

References 15 publications

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“…This is related to the blue shift of the fundamental , Figure b, and is also determined by the complexation shift of . Insight in this is obtained from unperturbed frequencies of monomer and complex, which were derived using the intensity method. − The observed intensities of and 2 needed for the analysis were determined by least squares fitting, using Gauss/Lorentz sum functions, of the region shown in Figure (parts b and d). The resulting unperturbed frequencies are collected in Table .…”

Section: Resultsmentioning

confidence: 99%

van der Waals Complexes between Carbonyl Fluoride and Boron Trifluoride Observed in Liquefied Argon, Krypton, and Nitrogen: A FTIR and ab Initio Study

Stolov¹,

Herrebout²,

Veken³

1998

J. Am. Chem. Soc.

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The IR spectra (4000-400 cm-1) of COF2/BF3 mixtures, dissolved in liquefied argon (LAr), krypton (LKr), and nitrogen (LN2), have been examined. In all spectra evidence was found for the formation of a 1:1 van der Waals complex. Using spectra recorded at several temperatures between 81 and 172 K the complexation enthalpies ΔH° in LAr, LKr, and LN2 were determined to be −11.8(3), −10.6(3), and −7.8(3) kJ mol-1, respectively. A theoretical study, using both density functional theory at the B3LYP/6-311++G(d,p) level and ab initio at the MP2/aug-cc-pVTZ level, indicates that the complexation can occur either via the oxygen or via a fluorine atom of COF2. From a comparison of the experimental and calculated frequencies it was concluded that the observed complex bands are due to a species in which the boron atom coordinates with the oxygen lone pairs. The complexation energy Δc E is obtained from the ΔH° by correcting for solvent influences, and thermal contributions equals −15.0(6) kJ mol-1. This value agrees well with the MP2/aug-cc-pVTZ level result, −12.4 kJ mol-1. The complexation entropy ΔS° has been found to be influenced by the solvent and is correlated with ΔH°. This correlation reflects the existence of the compensation effect for the thermodynamics of van der Waals complexes.

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Section: Resultsmentioning

confidence: 99%

van der Waals Complexes between Carbonyl Fluoride and Boron Trifluoride Observed in Liquefied Argon, Krypton, and Nitrogen: A FTIR and ab Initio Study

Stolov¹,

Herrebout²,

Veken³

1998

J. Am. Chem. Soc.

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“…Matsuura analyzed the Fermi resonance between ν ±1 6 and (ν 7 + ν 8 ) ∓2 [22]. Duncan et al [23] and later Matsuura et al [24] included the Coriolis resonance between ν 6 and ν 3 in their analyses. Paso et al [6] presented the latest, fairly comprehensive and quite accurate analysis of these bands.…”

Section: Introductionmentioning

confidence: 99%

Toward a global model of the interactions in low-lying states of methyl cyanide: rotational and rovibrational spectroscopy of the $v_4 = 1$ state and tentative interstellar detection of the $v_4 = v_8 = 1$ state in Sgr B2(N)

Müller,

Belloche,

Lewen

et al. 2021

Preprint

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Rotational spectra of methyl cyanide were recorded newly and were analyzed together with existing spectra to extend the global model of low-lying vibrational states and their interactions to 4 = 1 at 920 cm −1 . The rotational spectra cover large portions of the 36−1439 GHz region and reach quantum numbers J and K of 79 and 16, respectively. Information on the K level structure of CH 3 CN is obtained from IR spectra. A spectrum of 2ν 8 around 717 cm −1 , analyzed in our previous study, covered also the ν 4 band. The assignments in this band cover 880−952 cm −1 , attaining quantum numbers J and K of 61 and 13, respectively.The most important interaction of 4 = 1 appears to be with 8 = 3, ∆K = 0, ∆l = +3, a previously characterized anharmonic resonance. We report new analyses of interactions with ∆K = −2 and ∆l = +1, with ∆K = −4 and ∆l = −1, and with ∆K = −6 and ∆l = −3; these four types of interactions connect all l substates of 8 = 3 in energy to 4 = 1. A known ∆K = −2, ∆l = +1 interaction with 7 = 1 was also analyzed, and investigations of the ∆K = +1, ∆l = −2 and ∆K = +3, ∆l = 0 resonances with 8 = 2 were improved, as were interactions between successive states with 8 ≤ 3, mainly through new 8 ≤ 2 rotational data. A preliminary single state analysis of the 4 = 8 = 1 state was carried out based on rotational transition frequencies and on ν 4 + ν 8 − ν 8 hot band data. A considerable fraction of the K levels was reproduced within uncertainties in its entirety or in part, despite obvious widespread perturbations in 4 = 8 = 1.In addition to the interstellar detection of rotational transitions of methyl cyanide from within all vibrational states up to 4 = 1, we report the tentative detection of 4 = 8 = 1 toward the main hot molecular core of the protocluster Sagittarius B2(N) employing the Atacama Large Millimeter/submillimeter Array.

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“…Fermi resonance extensively exists in stretching overtone spectra and has been quantitatively analyzed in different approaches. ,− Unperturbed stretching energies with Fermi resonance were obtained from interpolation and extrapolation of the Birge−Sponer plot where the stretching mode parameters are obtained from the Birge−Sponer fit of the transitions without obvious Fermi resonance. , Winther et al suggested three methods to obtain the unperturbed frequencies from the perturbed frequencies at the fundamental transition for dicyanoaccetylene . One of their methods obtains unperturbed frequencies from the intensity ratio and the corresponding perturbed frequencies. , Our approach is similar in that we obtain the unperturbed frequencies from the perturbed frequencies and relative intensities for overtones in a two-level system model.…”

Section: Introductionmentioning

confidence: 99%

CH Stretching Overtone Spectra of Fluorine Substituted Toluenes

2003

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We have measured and analyzed the vapor phase CH stretching overtone spectra of 3,5-difluorotoluene, 2,3,5,6-tetrafluorotoluene, and 2,3,4,5,6-pentafluorotoluene. The aryl bands are complex due to Fermi resonance. We have used a two-level system model to analyze the Fermi resonance within the aryl bands. The aryl regions of the overtone spectra are "corrected" for Fermi resonance and interpreted as uncoupled stretching oscillators. The methyl band profiles are complex due to the coupling between CH stretching and methyl torsion. The methyl band profiles are simulated with a CH stretching methyl torsion model. The CH stretching modes are described by a harmonically coupled anharmonic oscillator local mode model, and the methyl torsion is described by a rigid rotor model. Simulation parameters are obtained from ab initio calculations with the HF/6-31G(d) method. Relative intensities of aryl and methyl contributions in the CH stretching overtone spectra in the region ∆V CH ) 2-5 are measured and calculated for these molecules. We have found that the methyl bands of 3,5-difluorotoluene are very similar to corresponding bands in toluene, 4-methylpyridine, p-xylene, and m-xylene. The methyl bands of 2,3,5,6-tetrafluorotoluene and 2,3,4,5,6-pentafluorotoluene are virtually identical to those of 2,6-difluorotoluene. Thus, the main factor that determines the structure in methyl CH stretching overtone spectra of these molecules is the nature of the groups adjacent to the methyl group. The aryl bands of these molecules are primarily affected by the nearest substituents.

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Analysis of theν₃,ν₆,ν₇+ν₈Fermi and Coriolis interacting band system in methyl cyanide

Cited by 31 publications

References 15 publications

van der Waals Complexes between Carbonyl Fluoride and Boron Trifluoride Observed in Liquefied Argon, Krypton, and Nitrogen: A FTIR and ab Initio Study

van der Waals Complexes between Carbonyl Fluoride and Boron Trifluoride Observed in Liquefied Argon, Krypton, and Nitrogen: A FTIR and ab Initio Study

Toward a global model of the interactions in low-lying states of methyl cyanide: rotational and rovibrational spectroscopy of the $v_4 = 1$ state and tentative interstellar detection of the $v_4 = v_8 = 1$ state in Sgr B2(N)

CH Stretching Overtone Spectra of Fluorine Substituted Toluenes

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