Baweja, ShefaliAntonelli, EleonoreHussain, SafiaFernández Ramos, AntonioKleiner, IsabelleSanz, M. EugeniaNguyen, Ha Vinh Lam2024-12-202024-12-202023-02-24Baweja, S., Antonelli, E., Hussain, S., Fernández-Ramos, A., Kleiner, I., Nguyen, H.V.L., Sanz, M.E.(2023). Revealing Internal Rotation and 14N Nuclear Quadrupole Coupling in the Atmospheric Pollutant 4-Methyl-2-nitrophenol: Interplay of Microwave Spectroscopy and Quantum Chemical Calculations. “Molecules”, vol. 28(5). https:// doi.org/10.3390/molecules280521531420-3049https://hdl.handle.net/10347/38247The 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.eng© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).Attribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/Rotational spectroscopyAb initio and density functional theory calculationsInternal rotationNuclear quadrupole couplingLarge-amplitude motio2391 Química ambientaljournal article10.3390/molecules28052153open access