Kinetics and mechanism of the reactions of OH radicals with p-nitroaniline in gas-phase and aqueous solution

The OH-initiated oxidation of p-nitroaniline (p-NA) was studied both in gas phase and aqueous solution. The calculated results show that addition reactions between p-NA and OH radicals are highly feasible in gas phase. OH addition to the ortho C of the amino group is the most favorable. The major products are p-nitrophenol (p-NP), 2-amino-5-nitrophenol, 5-amino-2-nitrophenol and p-aminophenol. The H atom of the amino group is the easiest one to be abstracted by OH radical. The undergoing degradation is investigated in the presence of O2, which generate oxygen-rich compounds including five-membered heterocycles or six-membered heterocycles and 2-amino-5-nitrophenol or 5-amino-2-nitrophenol. The effect of water solution on the title reactions was considered. The calculated results show that aqueous solution makes the addition reactions between p-NA and OH radical more uniform while H-abstraction reactions are not significant. The total rate constant of OH radicals with p-NA under 298 K, 1 atm is determined to be 6.97 × 10−11 cm3 molecule−1 s−1. With respect to OH radical, the life time of p-NA in atmosphere is estimated to be 4.1 h.