Formation of OH radicals in the gas phase reactions of O3 with a series of terpenes

Abstract

The gas phase reactions of O3 with ethene, isoprene, and a series of monoterpenes have been investigated at 296±2 K and atmospheric pressure of air in the presence of cyclohexane at concentrations sufficient to essentially totally scavenge any OH radicals formed. The expected products of the OH radical-initiated reaction of cyclohexane, cyclohexanone and cyclohexanol, were observed in all cases. The OH radical formation yields obtained from the gas phase reactions of O3 with alkanes were ethene, 0.12; isoprene, 0.27; camphene, ≤0.18; 3-carene, 1.06; limonene, 0.86; myrcene, 1.15; ocimene (a cis-, trans-mixture), 0.63; β-phellandrene, 0.14; α-pinene, 0.85; β-pinene, 0.35; sabinene, 0.26; and terpinolene, 1.03, all with estimated overall uncertainties of a factor of ~1.5. For α-pinene the effect of varying the water vapor concentration was investigated and no change in the OH radical formation yield was observed. -from Authors