Examining Intermolecular Interactions Between Hydrocarbons And Water: A Broadband Rotational Spectroscopic Study Of The Α-pinene – Water Complex

Hazrah, Arsh Singh

Permalink

https://hdl.handle.net/2142/116629 Copy

Description

Title

Examining Intermolecular Interactions Between Hydrocarbons And Water: A Broadband Rotational Spectroscopic Study Of The Α-pinene – Water Complex

Author(s)

Hazrah, Arsh Singh

Contributor(s)

• Jäger, Wolfgang
• Al-Jabiri, Mohamad H.

Issue Date

2022-06-22

Keyword(s)

Non-covalent interactions

Abstract

Released into the atmosphere by vegetation, biogenic volatile organic compounds (VOCs) contribute substantially to yearly carbon emission, amounting to approximately 1150 Tg of carbon per year.$^{1}$ $\alpha$-pinene, a bicyclic monoterpene, is not only one of the most abundant biogenic VOCs released, but also plays a critical role in the generation of secondary organic aerosol. Once released, $\alpha$-pinene can be photo-oxidized by atmospheric species such as ozone or various radical species.$^{2}$ Water is relatively abundant in the atmosphere and has therefore a high probability of a close contact with $\alpha$-pinene. Complexation with water may affect the reactivity with species such as ozone, thus altering product yield, and ultimately the rate of aerosol formation. It is difficult to predict a preferred structure for the $\alpha$-pinene-water cluster using chemical intuition alone, and a study of its structure and energetics can provide insights into intermolecular interactions between weakly-polar hydrocarbons and hydrogen bonding capable species, as well as data relevant to atmospheric processes. To experimentally identify $\alpha$-pinene-water clusters we used a chirped pulse Fourier transform microwave spectrometer in the 2-6 GHz range$^{3}$ and the experiments were supplemented with electronic structure calculations. Two potential conformers were theoretically identified, both of which involve the formation of an O-H --- $\pi$ bond between water and $\alpha$-pinene. However, only the higher energy conformer could be assigned experimentally. From various one-dimensional energy scans along internal rotation coordinates, the absence of the lower energy conformer is most likely due to a large amplitude O-H wagging motion, which leads to a partial dipole moment cancellation. The O-H --- $\pi$ interaction in both complexes was then visualized and quantified using non-covalent interactions$^{4}$ and natural bond orbital analyses$^{5}$, respectively. 1. A. Guenther, C. N. Hewitt, D. Erickson, R. Fall, C. Geron, T. Graedel, P. Harley, L. Klinger, M. Lerdau and W. A. McKay, J. Geophys. Res. Atmos., 1995, 100, 8873–8892.; 2. J. H. Seinfeld and J. F. Pankow, Annu. Rev. Phys. Chem., 2003, 54, 121–140.; 3. N. A. Seifert, J. Thomas, W. Jäger and Y. Xu, Phys. Chem. Chem. Phys., 2018, 20, 27630–27637.; 4. J. Contreras-García, E. R. Johnson, S. Keinan, R. Chaudret, J.-P. Piquemal, D. N. Beratan and W. Yang, J. Chem. Theory Comput., 2011, 7, 625–632.; 5. E. D. Glendening, C. R. Landis and F. Weinhold, J. Comput. Chem., 2013, 34, 1429–1437.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Handle URL

https://hdl.handle.net/2142/116629&&

DOI

https://doi.org/10.15278/isms.2022.WM08

Copyright and License Information

Copyright 2022 held by the authors

Owning Collections