Large Amplitude Torsions in Nitrotoluene Isomers Studied by Rotational Spectroscopy and Quantum Chemistry Calculations |
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Authors: | Dr Anthony Roucou Dr Manuel Goubet Prof Isabelle Kleiner Dr Sabath Bteich Prof Arnaud Cuisset |
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Institution: | 1. Université du Littoral Côte d'Opale, UR 4493, LPCA, Laboratoire de Physico-Chimie de l'Atmosphère, F-59140 Dunkerque, France;2. Univ. Lille, CNRS, UMR8523 – PhLAM – Physique des Lasers Atomes et Molécules, F-59000 Lille, France;3. Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS UMR 7583, Université Paris-Est Créteil & Université de Paris, Institut Pierre Simon Laplace (IPSL), 61 avenue du Général de Gaulle, F-94010 Créteil cedex, France |
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Abstract: | Rotational spectra of ortho-nitrotoluene (2-NT) and para-nitrotoluene (4-NT) have been recorded at low and room temperatures using a supersonic jet Fourier Transform microwave (MW) spectrometer and a millimeter-wave frequency multiplier chain, respectively. Supported by quantum chemistry calculations, the spectral analysis of pure rotation lines in the vibrational ground state has allowed to characterise the rotational energy, the hyperfine structure due to the 14N nucleus and the internal rotation splittings arising from the methyl group. For 2-NT, an anisotropic internal rotation of coupled −CH3 and −NO2 torsional motions was identified by quantum chemistry calculations and discussed from the results of the MW analysis. The study of the internal rotation splittings in the spectra of three NT isomers allowed to characterise the internal rotation potentials of the methyl group and to compare them with other mono-substituted toluene derivatives in order to study the isomeric influence on the internal rotation barrier. |
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Keywords: | Explosive taggant Large amplitude torsions Molecular dynamics Nitrotoluene isomers Rotational spectroscopy |
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