Vibrational Mode Assignment of α-Pinene by Isotope Editing: One Down, Seventy-One To Go

Journal Article · Thu May 05 00:00:00 EDT 2016 · Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory

DOI:https://doi.org/10.1021/acs.jpca.6b01995· OSTI ID:1337273

Upshur, Mary Alice; Chase, Hilary M.; Strick, Benjamin F.; Ebben, Carlena J.; Fu, Li; Wang, Hongfei; Thomson, Regan J.; Geiger, Franz M.

This study aims to reliably assign the vibrational sum frequency generation (SFG) spectrum of α-pinene at the vapor/solid interface using a method involving deuteration of various methyl groups. The synthesis of five different deuterated isotopologues of α-pinene is presented in order to determine the impact that removing contributions from methyl group C$$-$$H oscillators has on its SFG response. 0.6 cm^-1 Resolution SFG spectra of these isotopologues show varying degrees of differences in the C–H stretching region when compared to the SFG response of unlabeled α-pinene. The largest spectral changes were observed for the isotopologue containing a fully deuterated vinyl methyl group. Noticeable losses in signal intensities allow us to reliably assign the 2860 cm^-1 peak to the vinyl methyl symmetric stretch. Furthermore, upon removing the vinyl methyl group entirely by synthesizing apopinene, the steric influence of the unlabeled C₉H₁₄ fragment on the SFG response of α-pinene SFG can be readily observed. The work presented here brings us one step closer to understanding the vibrational spectroscopy of α-pinene.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1337273
• Report Number(s): PNNL-SA-116446; 48842; KP1704020
• Journal Information: Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, Vol. 120, Issue 17; ISSN 1089-5639
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

Sum frequency generation
alpha-pinene
spectra
Environmental Molecular Sciences Laboratory