Infrared Spectra of Cyanoacetaldehyde (NCCH2CHO): A Potential Prebiotic Compound of Astrochemical Interest

Authors

  • Dr. Abdessamad Benidar,

    Corresponding author
    1. Institut de Physique de Rennes, CNRS UMR 6251, Université de Rennes 1, 35042 Rennes (France)
    • Institut de Physique de Rennes, CNRS UMR 6251, Université de Rennes 1, 35042 Rennes (France)
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  • Prof. Robert Georges,

    1. Institut de Physique de Rennes, CNRS UMR 6251, Université de Rennes 1, 35042 Rennes (France)
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  • Dr. Jean-Claude Guillemin,

    Corresponding author
    1. Institut des Sciences Chimiques de Rennes, École Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, Avenue du Général Leclerc, CS 50837, 35708 Rennes Cedex 7 (France)
    • Institut des Sciences Chimiques de Rennes, École Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, Avenue du Général Leclerc, CS 50837, 35708 Rennes Cedex 7 (France)
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  • Prof. Otilia Mó,

    1. Departamento de Quimica, Modulo 13, Universidad Autonoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, 28049-Madrid (Spain)
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  • Prof. Manuel Yáñez

    Corresponding author
    1. Departamento de Quimica, Modulo 13, Universidad Autonoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, 28049-Madrid (Spain)
    • Departamento de Quimica, Modulo 13, Universidad Autonoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, 28049-Madrid (Spain)
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Abstract

Cyanoacetaldehyde (NC[BOND]CH2CH[DOUBLE BOND]O) and its isomer, cyanovinylalcohol (NC[BOND]CH[DOUBLE BOND]CH[BOND]OH), as possible components of the interstellar medium, comets, or planetary atmospheres, exist in equilibrium in the gas phase, although the latter compound is very much in the minority (2 %). The recording and analysis of the gas-phase infrared spectrum of the former compound within the 4000–500 cm−1 spectroscopic range and the potential presence of the latter isomer, which could be vital for their detection in these media, are reported. CCSD(T) and G4 high-level ab initio methods, as well as density functional theory calculations, predict the existence of two stable rotamers of cyanoacetaldehyde. The global minimum has a structure with an unusual O-C-C-C dihedral angle (150°) that falls between the antiperiplanar (180°) and anticlinal forms (120°). The second rotamer, which is about 4.0 kJ mol−1 less stable in terms of free energy, has a planar structure that corresponds to the synperiplanar form (O-C-C-C dihedral angle: 0°). The absorption vibrational bands of the two aldehyde rotamers that are present in the mixture lead to a spectrum with a very complex structure in the region of deformation movements, in which several low-intensity bands overlap. A complete and unambiguous assignment of the experimental spectrum has been achieved by using the calculated harmonic and anharmonic vibrational frequencies.

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