Experimental and theoretical study of the reaction of OH radical with sabinene.

The gas phase sabinene + OH reaction is studied both experimentally and theoretically. Product yields from the reaction of sabinene with OH radicals have been measured in the absence of NOx in the UCC chamber (Cork, Ireland) and in the presence of NOx in the LISA chamber. Three primary carbonyl compounds were observed and quantified: acetone in [(24 +/- 6)%], formaldehyde in [(25 +/- 6)%] and sabinaketone in [(20 +/- 6)%]. The simultaneous quantification of these compounds is one of the major results of this work. The mechanism of product formation for this reaction has been studied using the quantum chemical DFT-B3LYP (6-31G(d,p) method. According to these calculations, the H-atom abstraction channel from sabinene by OH in the initial oxidation step may be taken into account to explain the acetone production. Sabinaketone and formaldehyde are mainly products of the addition channels of OH on the -C=CH2 double bond of sabinene. This is the first theoretical work on the title reaction.