Revealing Internal Rotation and <sup>14</sup>N Nuclear Quadrupole Coupling in the Atmospheric Pollutant 4-Methyl-2-nitrophenol: Interplay of Microwave Spectroscopy and Quantum Chemical Calculations
Shefali Baweja,
Eleonore Antonelli,
Safia Hussain,
Antonio Fernández-Ramos,
Isabelle Kleiner,
Ha Vinh Lam Nguyen,
M. Eugenia Sanz
Affiliations
Shefali Baweja
Department of Chemistry, King’s College London, Britannia House, 7 Trinity Street, London SE1 1DB, UK
Eleonore Antonelli
Université Paris Est Créteil and Université Paris Cité, CNRS, LISA, F-94010 Créteil, France
Safia Hussain
Department of Chemistry, King’s College London, Britannia House, 7 Trinity Street, London SE1 1DB, UK
Antonio Fernández-Ramos
Departamento de Química Física and Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS), Jenaro de la Fuente s/n, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain
Isabelle Kleiner
Université Paris Cité and Université Paris Est Créteil, CNRS, LISA, F-75013 Paris, France
Ha Vinh Lam Nguyen
Université Paris Est Créteil and Université Paris Cité, CNRS, LISA, F-94010 Créteil, France
M. Eugenia Sanz
Department of Chemistry, King’s College London, Britannia House, 7 Trinity Street, London SE1 1DB, UK
The structure and interactions of oxygenated aromatic molecules are of atmospheric interest due to their toxicity and as precursors of aerosols. Here, we present the analysis of 4-methyl-2-nitrophenol (4MNP) using chirped pulse and Fabry–Pérot Fourier transform microwave spectroscopy in combination with quantum chemical calculations. The rotational, centrifugal distortion, and 14N nuclear quadrupole coupling constants of the lowest-energy conformer of 4MNP were determined as well as the barrier to methyl internal rotation. The latter has a value of 106.4456(8) cm−1, significantly larger than those from related molecules with only one hydroxyl or nitro substituent in the same para or meta positions, respectively, as 4MNP. Our results serve as a basis to understand the interactions of 4MNP with atmospheric molecules and the influence of the electronic environment on methyl internal rotation barrier heights.
