O-TOLUIC ACID MONOMER AND MONOHYDRATE: ROTATIONAL SPECTRA, STRUCTURES, AND ATMOSPHERIC IMPLICATIONS

Schnitzler, Elijah G

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https://hdl.handle.net/2142/79322 Copy

Description

Title

O-TOLUIC ACID MONOMER AND MONOHYDRATE: ROTATIONAL SPECTRA, STRUCTURES, AND ATMOSPHERIC IMPLICATIONS

Author(s)

Schnitzler, Elijah G

Contributor(s)

• Jäger, Wolfgang
• Zenchyzen, Brandi L M

Issue Date

24-Jun-15

Keyword(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.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

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http://hdl.handle.net/2142/79322

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