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

Abstract : Cyanoacetaldehyde (NC-CH2CH=O) and its isomer, cyanovinylalcohol (NC-CH=CH-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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Submitted on : Monday, March 10, 2014 - 9:36:56 AM
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Abdessamad Benidar, Robert Georges, Jean-Claude Guillemin, Otilia Mó, Manuel Yáñez. Infrared Spectra of Cyanoacetaldehyde (NCCH2CHO): A Potential Prebiotic Compound of Astrochemical Interest. ChemPhysChem, Wiley-VCH Verlag, 2013, 14 (12), pp.2764-2771. ⟨10.1002/cphc.201300354⟩. ⟨hal-00957287⟩

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