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Large Amplitude Torsions in Nitrotoluene Isomers Studied by Rotational Spectroscopy and Quantum Chemistry Calculations
Author(s) -
Roucou Anthony,
Goubet Manuel,
Kleiner Isabelle,
Bteich Sabath,
Cuisset Arnaud
Publication year - 2020
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.202000591
Subject(s) - quantum chemistry , computational chemistry , rotational spectroscopy , chemistry , spectroscopy , quantum chemical , amplitude , quantum , nuclear magnetic resonance spectroscopy , physics , organic chemistry , quantum mechanics , molecule , supramolecular chemistry
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 14 N nucleus and the internal rotation splittings arising from the methyl group. For 2‐NT, an anisotropic internal rotation of coupled −CH 3 and −NO 2 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.