Atmospheric lifetimes and fates of selected fragrance materials and volatile model compounds.

Abstract

Fragrance materials are semivolatile organic compounds widely used in consumer products. Despite their generally low volatility, it is expected that a fraction of these compounds will volatilize into the atmosphere, where they can photolyze, react with OH radicals, NO3 radicals and O3, and/or undergo wet and dry deposition. Using relative rate methods, rate constants have been measured at 296 +/- 2 K for the gas-phase reactions of OH radicals, NO3 radicals, and 03 with the fragrance materials 1-(1,2,3,4,5,6,7,8-octahydro-2,3,8,8-tetramethyl-2-naphthalenyl)ethanone (OTNE), acetyl cedrene [(3R-(3a,3ab,7b,8aa))-1-(2,3,4,7,8,8a-hexahydro-3,6,8,8-tetramethyl-1H-3a,7-methanoazulen-5-yl)ethan-1-one], and HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethycyclopenta-[gamma]-2-benzopyran) as well as with isochroman which is structurally related to HHCB. Measured rate constants (in cm3 molecule(-1) s(-1) units) are OH radical reactions [OTNE, (9.85 +/- 0.88) x 10(-11); acetyl cedrene, (7.7 +/- 1.6) x 10(-11); HHCB, (2.6 +/- 0.6) x 10(-11); and isochroman, (3.7 +/- 0.6) x 10(-11)], NO3 radical reactions [OTNE, (1.71 +/- 0.19) x 10(-11) and acetyl cedrene, (4.1 +/- 1.0) x 10(-15)], and O3 reactions [OTNE, (2.1 +/- 0.5) x 10(-18) and acetyl cedrene, <2.2 x 10(-18)] where the error limits are two least-squares standard deviations. Rate constants for the OH radical reactions predicted by a structure-reactivity estimation method agree well with the measured values. The dominant tropospheric loss processes for the compounds studied are calculated to be in a reaction with OH radicals during daytime and, for OTNE and acetyl cedrene, with NO3 radicals during nighttime. The calculated atmospheric lifetimes due to daytime reaction with the OH radical are a few hours or less for the fragrance materials studied and indicate that these specific compounds will not undergo long-range transport in the atmosphere.