Rate Constants for the Gas-Phase Reactions of Ozone and Nitrate Radicals with the Sesquiterpenes: Valencene and Farnesol

Sesquiterpenes are constituents of a variety of essential oils that are used in flavorings, perfumes, personal care, and cleaning products. Two sesquiterpenes that are commonly used as indoor fragrances are valencene and farnesol. Knowing the reaction rate constants of these chemicals with ozone (O-3) and nitrate radical (NO3 center dot) is an important factor in determining their fate indoors. In this study, the bimolecular rate constants of k(O3+ valencene) (0.35 +/- 0.9)x10(-16), k(O3+ farnesol) (21 +/- 5.2)x10(-16), k(NO) 3 center dot+ valencene (7.9 +/- 2.0)x10(-12), and k(NO3)(+ farnesol)(center dot) (44 +/- 11)x10(-12) cm 3 molecule(-1)s(-1) were measured using the relative rate technique at 297 +/- 3 K and 1 atm total pressure. Using the rate constants reported here and measured/modeled indoor concentrations of O-3 and NO3 center dot (20 ppb and 1 ppt, respectively), pseudo-first-order-rate lifetimes k '(O3+ valencene) (0.06), k '(O3+ farnesol) (3.8), k '(NO 3)+ valencene (0.7), and k '(NO 3 center dot+ farnesol) (3.9)h(-1) were determined.