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

Autor:	Upshur MA; Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States., Chase HM; Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States., Strick BF; Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States., Ebben CJ; Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States., Fu L; William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99352, United States., Wang H; William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99352, United States., Thomson RJ; Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States., Geiger FM; Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
Jazyk:	angličtina
Zdroj:	The journal of physical chemistry. A [J Phys Chem A] 2016 May 05; Vol. 120 (17), pp. 2684-90. Date of Electronic Publication: 2016 Apr 26.
DOI:	10.1021/acs.jpca.6b01995
Abstrakt:	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 deuterated isotopologues of α-pinene is presented 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.
Databáze:	MEDLINE
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