Reaction of Naphthalene and Its Derivatives with Hydroxyl Radicals in the Gas Phase

Abstract

Naphthalene is the most abundant polycyclic aromatic hydrocarbon (PAH) found in urban air. It is reactive in the atmosphere under ambient conditions, its chief reaction partner being the hydroxyl radical, OH•. In this work, the reactions of OH• with naphthalene, 1- and 2-naphthol, and 1- and 2-nitronaphthalene were studied in a 9.4 m3 smog chamber. Relative rates of reaction accorded well with previous studies and allowed estimates to be made of the atmospheric lifetimes of these compounds. Numerous oxidation products were identified, and mechanisms proposed for their formation were based on the further transformation of benzocyclohexadienyl radicals formed by addition of OH• to naphthalene. The naphthols and nitronaphthalenes were deduced not to be on the major reaction pathway to the more oxidized products. Because of the high reactivity of PAH in air, we suggest that priority be given to identifying and quantitating their reaction products, some of which may be relatively persistent air toxics.