Products and mechanisms of the reactions of a series of hydrofluoroalkenes initiated by OH radicals

M. B. BLANCO ; A. LADINO CARDONA; E. GAONA-COLMÁN; I. BARNES

Simposio; The 25th International Symposium on Gas Kinetics; 2018

β-Ocimene and camphene are monoterpenes, which emissions has been detected from several types of vegetation (13). In the troposphere, biogenic volatile organic compounds (BVOCs) can react with the main atmospheric oxidants (OH radicals, NO3 radicals and O3 molecules) leading to the formation of variety groups of product species and participate in the formation of tropospheric ozone and secondary organic aerosols (4). In this study, the rate coefficients for the gas-phase reaction of Cl atoms with β-ocimene and camphene were measured using the relative rate method at 298 K and 760 Torr. The experiments were performed in a long-path atmospheric chamber coupled to Fourier transformed infrared spectroscopy. The obtained rate coefficients are k(β-ocimene + Cl)= (5.5 ± 0.9)××10-10 cm3 molecule-1 s-1 and k(camphene + Cl)= (3.2 ± 0.5)××10-10 cm3 molecule-1 s-1. In addition, products identification has been performed at 298 K and 760 Torr in the absence of NOx using an 80 L collapsible Teflon chamber with Gas-Chromatography and Mass Spectrometer. In order to identify carbonyl products, the samples for each studied reaction were derivatized on fiber using the SPME technique and PFBHA as derivatizing agent. For the reaction of β-ocimene with Cl atoms, acetone was positively identified as reaction product. Acetone and formaldehyde were identified as reaction products for the reaction of camphene and Cl atoms. The branching ratios for the addition of Cl atom to the structures of the studied monoterpenes have been estimated through a theoretical calculation using M06/cc-pVTZ and CBS-QB3 functions. Mechanisms are proposed and atmospheric implications are discussed.