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Title:O-TOLUIC ACID MONOMER AND MONOHYDRATE: ROTATIONAL SPECTRA, STRUCTURES, AND ATMOSPHERIC IMPLICATIONS
Author(s):Schnitzler, Elijah G
Contributor(s):J�ger, Wolfgang; Zenchyzen, Brandi L M
Subject(s):Non-covalent interactions
Abstract:Clusters of carboxylic acids with water, sulfuric acid, and other atmospheric species potentially increase the rate of new particle formation in the troposphere.footnote{F. Riccobono, textit{et al.}, textit{Science}, textbf{344}, 717 (2014).}$^{,}$footnote{R. Zhang, textit{et al.}, textit{Science}, textbf{304}, 1487 (2004).} Here, we present high-resolution pure rotational spectra of textit{o}-toluic acid and its complex with water in the range of 5-14 GHz, measured with a cavity-based molecular beam Fourier-transform microwave spectrometer. In both the monomer and the complex, the carboxylic acid functional group adopts a textit{syn-} conformation, with the acidic proton oriented away from the aromatic ring. In the complex, water participates in two hydrogen bonds, forming a six-membered intermolecular ring. Despite its large calculated textit{c}-dipole moment, no textit{c}-type transitions were observed for the complex, because of a large amplitude �wagging� motion of the unbound hydrogen of water, similar to the case of the benzoic acid-water complex.footnote{E. G. Schnitzler and W. J�ger, textit{Phys. Chem. Chem. Phys.}, textbf{16}, 2305 (2014).} No methyl internal rotation splittings were observed, consistent with a high barrier (7 kJ mol$^{-1}$) calculated for the monomer at the B3LYP/6-311++G(d,p) level of theory. Using statistical thermodynamics, experimental rotational constants were combined with a theoretical frequency analysis and binding energy to give an estimate of the percentage of hydrated acid in the atmosphere under various conditions.
Issue Date:24-Jun-15
Publisher:International Symposium on Molecular Spectroscopy
Citation Info:ACS
Genre:CONFERENCE PAPER/PRESENTATION
Type:Text
Language:English
URI:http://hdl.handle.net/2142/79322
Date Available in IDEALS:2016-01-05


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