Acetaldehyde: Harmonic Frequencies, Force Field, and Infrared Intensities

Wiberg, Kenneth B.; Thiel, Yvonne; Goodman, Lionel; Leszczyński, Jerzy

doi:10.1021/j100038a016

Cited by 43 publications

(32 citation statements)

References 6 publications

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“…61 The broad shape of this band (see Figure 6) indicates interaction of acetaldehyde in the matrix cage where it was formed either with HCN or azide.…”

Section: Uv-irradiation Experimentsmentioning

confidence: 98%

Tautomer Selective Photochemistry in 1-(Tetrazol-5-yl)ethanol

et al. 2010

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A combined matrix isolation FTIR and theoretical DFT/B3LYP/6-311++G(d,p) study of the molecular structure and photochemistry of 1-(tetrazol-5-yl)ethanol [1-TE] was performed. The potential energy surface landscapes of the 1H and 2H tautomers of the compound were investigated and the theoretical results were used to help characterize the conformational mixture existing in equilibrium in the gas phase prior to deposition of the matrices, as well as the conformers trapped in the latter. In the gas phase, at room temperature, the compound exists as a mixture of 12 conformers (five of the 1H tautomer and seven of the 2H tautomer). Upon deposition of the compound in an argon matrix at 10 K, only three main forms survive, because the low barriers for conformational isomerization allow extensive conformational cooling during deposition. Deposition of the matrix at 30 K led to further simplification of the conformational mixture with only one conformer of each tautomer of 1-TE surviving. These conformers correspond to the most stable forms of each tautomer, which bear different types of intramolecular H-bonds: 1H-I has an NH · · · O hydrogen bond, whereas 2H-I has an OH · · · N hydrogen bond. Upon irradiating with UV light (λ > 200 nm), a matrix containing both 1H-I and 2H-I forms, an unprecedented tautomer selective photochemistry was observed, with the 2H tautomeric form undergoing unimolecular decomposition to azide + hydroxypropanenitrile and the 1H-tautomer being photostable.

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“…61 The broad shape of this band (see Figure 6) indicates interaction of acetaldehyde in the matrix cage where it was formed either with HCN or azide.…”

Section: Uv-irradiation Experimentsmentioning

confidence: 98%

Tautomer Selective Photochemistry in 1-(Tetrazol-5-yl)ethanol

et al. 2010

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“…No rotational transitions in vibrationally excited levels of acetaldehyde were found in the ± 2 GHz spectral range around the 404 -303 transition of the vibrational ground state molecules. We attribute the existence of such highly efficient vibrational cooling in acetaldehyde to the internal CH3 rotor, with its 143 cm -1 rotor frequency [81,82], which may facilitate energy transfer between excited vibrational levels and the translational motion of the cold carrier gas [88].…”

Section: Ch3chomentioning

confidence: 99%

Chirped-pulse millimeter-wave spectroscopy for dynamics and kinetics studies of pyrolysis reactions

Prozument

Park

Shaver

et al. 2014

Phys. Chem. Chem. Phys.

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A Chirped-Pulse millimeter-Wave (CPmmW) spectrometer is applied to the study of chemical reaction products that result from pyrolysis in a Chen nozzle heated to 1000-1800 K. Millimeter-wave rotational spectroscopy unambiguously determines, for each polar reaction product, the species, the conformers, relative concentrations, conversion percentage from precursor to each product, and, in some cases, vibrational state population distributions. A chirped-pulse spectrometer can, within the frequency range of a single chirp, sample spectral regions of up to ∼10 GHz and simultaneously detect many reaction products. Here we introduce a modification to the CPmmW technique in which multiple chirps of different spectral content are applied to a molecular beam pulse that contains the pyrolysis reaction products. This technique allows for controlled allocation of its sensitivity to specific molecular transitions and effectively doubles the bandwidth of the spectrometer. As an example, the pyrolysis reaction of ethyl nitrite, CH3CH2ONO, is studied, and CH3CHO, H2CO, and HNO products are simultaneously observed and quantified, exploiting the multi-chirp CPmmW technique. Rotational and vibrational temperatures of some product molecules are determined. Subsequent to supersonic expansion from the heated nozzle, acetaldehyde molecules display a rotational temperature of 4 ± 1 K. Vibrational temperatures are found to be controlled by the collisional cooling in the expansion, and to be both species- and vibrational mode-dependent. Rotational transitions of vibrationally excited formaldehyde in levels ν4, 2ν4, 3ν4, ν2, ν3, and ν6 are observed and effective vibrational temperatures for modes 2, 3, 4, and 6 are determined and discussed.

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“…(1) and the analysis discussed below are listed in Tables I and II (omitting, in acetaldehyde, modes with energies above the C=O stretch). The elastic rates, Γ e ν , were calculated with experimental IR data [15,16], using Eq. (7) of Ref.…”

Section: Lz12933 R Ementioning

confidence: 99%

Role of Vibrational Dynamics in Resonant Positron Annihilation on Molecules

et al. 2013

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Vibrational Feshbach resonances are dominant features of positron annihilation for incident positron energies in the range of the molecular vibrations. Studies in relatively small molecules are described that elucidate the role of intramolecular vibrational energy redistribution into near-resonant multimode states, and the subsequent coupling of these modes to the positron continuum, in suppressing or enhancing these resonances. The implications for annihilation in other molecular species, and the necessary ingredients of a more complete theory of resonant positron annihilation, are discussed.

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Acetaldehyde: Harmonic Frequencies, Force Field, and Infrared Intensities

Cited by 43 publications

References 6 publications

Tautomer Selective Photochemistry in 1-(Tetrazol-5-yl)ethanol

Tautomer Selective Photochemistry in 1-(Tetrazol-5-yl)ethanol

Chirped-pulse millimeter-wave spectroscopy for dynamics and kinetics studies of pyrolysis reactions

Role of Vibrational Dynamics in Resonant Positron Annihilation on Molecules

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