The conformational landscape of 2-Pinen-10-ol and its water complex
Biogenic volatile organic compounds (BVOCs) are emitted in large quantities into the earth atmosphere and play a major role in the atmospheric chemistry. Monoterpenes (C10H16) represent 11% of the global BVOCs emission.1 Our group recently investigated the hydration of endo-fenchol in the gas phase a combination of Fourier transform microwave spectroscopy (FP-FTMW) coupled to a supersonic jet expansion and theoretical calculations. One conformer was observed and the role of the hydrogen bond in the stabilization of the observed structure was described.2 To go one step further, we considered 2-Pinen-10-ol. The conformational landscape of the monoterpene alcohol 2-Pinen-10-ol (6,6-Dimethylbicyclo[3.1.1]hept-2-ene-2-methanol) has been studied recently, and three conformers were observed and assigned to calculated structures.3 In the present work, the hydrogen bonding linking 2-Pinen-10-ol to water has been investigated. A similar approach combining quantum chemical calculations with FP-FTMW spectroscopy was employed.4,5 Five structures have been calculated below 8 kJ. Only one monohydrated conformer has been observed and assigned to a calculated structure. In addition the conformational landscape of the monomer has been reinvestigated. Geometry optimizations and harmonic vibrational frequency calculations were performed in order to characterize the equilibrium structure of conformers. Among the nine predicted structures, four have been observed, analyzed and identified. In addition, Deuteration of hydroxyl groups (OD) have been also studied which led to the determination of rs geometry and confirm the identity of the observed species.6
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6. 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, the European Funds for Regional Economic Development (FEDER), by the French Ministère de l’Enseignement Supérieur et de la Recherche. It is a contribution to the CPER research Project CLIMIBIO.