Rapid Gas-Phase Autoxidation of Nicotine in the Atmosphere.

Nicotine is the most abundant alkaloid chemical in smoke emission. In this work, we investigated the gas-phase oxidation mechanism of nicotine initiated by its reactions with the OH radical and ozone. Both initiation reactions start dominantly by hydrogen atom abstractions from the C1, C3, and -CH groups of the methylpyrrolidinyl group and form radicals nicotinyl-1, nicotinyl-3, and nicotinyl-6, respectively. The nicotinyl radicals would recombine rapidly with O, forming RO with rapid intramolecular hydrogen-atom transfers (HATs) with rate coefficients from 4 s to greater than 10 s. The rapid HATs in peroxy radicals suggest rapid autoxidation of nicotine in the gas phase. Formation of HCNO and HC(O)NH, being observed in previous studies, arises likely from secondary reactions or photolysis of intermediate products.