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Title:Intramolecular Interactions Within 1- And 2-naphthol: A Rotational Spectroscopic And Theoretical Study
Author(s):Hazrah, Arsh Singh
Contributor(s):Jäger, Wolfgang; Kraka, Elfi; Seifert, Nathan A.; Nanayakkara, Sadisha
Subject(s):Structure determination
Abstract:1- and 2-naphthol, hydroxy-derivatives of naphthalene, the simplest polycyclic aromatic hydrocarbon, are used as precursors in the dye, perfume, insecticide, and pharmaceutical industries.$^{1}$ Recently polyaromatic hydrocarbons (PAHs) such as naphthol have been examined for their complex intermolecular interplay within dimer structures.$^{2}$ To further build on previous PAHs studies we present a combined spectroscopic and theoretical study of 1- and 2-naphthol. The microwave spectra of the 1-naphthol and 2-naphthol monomers were measured using a chirped-pulse Fourier transform microwave spectrometer in the 2-6 GHz range. Spectroscopic assignments of the cis- and trans-conformers of 1-naphthol and 2-naphthol are supported by results from electronic structure calculations. Spectra of ten $^{13}$C isotopologues were identified and analyzed for all four species. This allowed for the determination of substitution structures and so-called semi-experimental effective structures. The theoretical results show that the OH group of cis-1-naphthol points ~ $6^{\circ}$ out of plane, which is consistent with the difference in inertial defect between cis- and trans-1-naphthol. For cis-1-naphthol, NCI$^{3}$ and QTAIM$^{4}$ analyses resulted in a bond critical point between the hydroxyl group H-atom and the close H-atom in the neighbouring ring, suggesting a bonding interaction. To confirm or deny this hypothesis, local mode analyses were carried out to obtain a more in-depth assessment of the O-H bond strengths. Compared to trans-1-naphthol, the strength of the O-H bond is much stronger in cis-1-naphthol. This is reflected in a blue shift of the O-H stretching frequency and is consistent with the traditional notion of a steric repulsion rather than a bonding interaction. 1. H. Shindy, Chem. Int, 2016, 2, 2016.; 2. N. A. Seifert, A. S. Hazrah and W. J\"{a}ger, J. Phys. Chem. Lett., 2019, 10, 2836-2841.; 3. E. Johnson, S. Keinan, P. Mori-Sánchez and J. Contreras-García, J. Am. Chem. Soc., 2010, 2010, 132.; 4. R. F. Bader, Chemical Reviews, 1991, 91, 893-928.
Issue Date:2021-06-24
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Date Available in IDEALS:2021-09-24

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