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Title:New Investigation Of The Rotational Spectrum Of Sabinene
Author(s):Dréan, Pascal
Contributor(s):Huet, Therese R.; Chrayteh, Mhamad
Subject(s):Structure determination
Abstract:Sabinene (\chem{C_{10}H_{16}}-4-methylene-1-(1-methylethyl)bicyclo[3.1.0]hexane) is a bicyclic monoterpene with an exocyclic double bond. It is one of the main biogenic volatile organic compound. In Europe, it is emitted in the troposphere by trees such as \textit{Quercus ilex}, \textit{Betula pendula}, and \textit{Fagus sylvatica} with an estimated flux of 20 Tg.yr$^{-1}$. It acts as precursor of secondary organic aerosols through several oxidation reactions. A first investigation of the low resolution rotational spectrum of sabinene was performed 40 years ago leading to the determination of the $(B+C)$ combination of rotational constants of the parent species.[1] From this unique data, and within numerous assumptions, the dihedral angle $\phi$ defining the boat arrangement of the five-membered ring was determined ($55^{\circ}$), but it is not in agreement with the typical values observed in molecules based on bicyclo[3.1.0]hexane.[2] In this work, the rotational spectrum of sabinene along with its gas phase structure were reinvestigated theoretically and experimentally employing a combination of quantum chemical calculations and Fourier transform microwave spectroscopy coupled to a supersonic jet expansion in the 2-20 GHz frequency region. The spectra of the parent species and of all singly substituted $^{13}$C isotopologues have been analysed in natural abundance. The 11 sets of rotational constants allowed to determine the partial substitution and effective structures of sabinene. They are in fair agreement with the optimized ones at the B3LYP, M06-2X and MP2 levels associated with the 6-311++G(d,p) basis set. The dihedral angle $\phi$ was determined to be $26.9^{\circ}$. [1] Z. Kisiel, A. C. Legon, Conformations of some bicyclic monoterpenes based on bicyclo [3.1.0] hexane from their low-resolution microwave spectra, J. Am. Chem. Soc. 100 (1978) 8166–8169. [2] E. J. Ocola, L. A. Wieding, S. Adams, J. Laane, Theoretical study of structures and ring-puckering potential energy functions of bicylo [3.1.0] hexane and related molecules, J. Phys. Chem. A 122 (2018) 5970–5977. The present work was funded by the French ANR Labex CaPPA through the PIA under contract ANR-11-LABX-0005-01, by the Regional Council Hauts de France, by the European Funds for Regional Economic Development (FEDER), and by the French Minist\`{e}re de l'Enseignement Sup\'{e}rieur et de la Recherche. It is a contribution to the CPER research Project CLIMIBIO.
Issue Date:2021-06-24
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Date Available in IDEALS:2021-09-24

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