Photochemical Formation of Nitrite and Nitrous Acid (HONO) upon Irradiation of Nitrophenols in Aqueous Solution and in Viscous Secondary Organic Aerosol Proxy

Abstract

Irradiated nitrophenols can produce nitrite and nitrous acid (HONO) in bulk aqueous solutions and in viscous aqueous films, simulating the conditions of a high-solute-strength aqueous aerosol, with comparable quantum yields in solution and viscous films (10-10 in the case of 4-nitrophenol) and overall reaction yields up to 0.3 in solution. The process is particularly important for the para-nitrophenols, possibly because their less sterically hindered nitro groups can be released more easily as nitrite and HONO. The nitrophenols giving the highest photoproduction rates of nitrite and HONO (most notably, 4-nitrophenol and 2-methyl-4-nitrophenol) could significantly contribute to the occurrence of nitrite in aqueous phases in contact with the atmosphere. Interestingly, dew-water evaporation has shown potential to contribute to the gas-phase HONO levels during the morning, which accounts for the possible importance of the studied process.

Beyond esterase‐like activity of serum albumin. Histidine‐(nitro)phenol radical formation in conversion cascade of p‐nitrophenyl acetate and the role of infrared light

“…The mechanism proposed in the literature for the photolysis of NP in aqueous solution involves light-induced breaking of O-H bond and formation of phenoxyl radical, which can yield HNO 2 in further reaction of nitro group with water. 12 In fact, a detailed inspection of the spectral signatures evolving in our experimental system suggests formation of phenoxyl radical (Figure 2). Its presence is marked by characteristic pair of the UV-Vis peaks of similar intensity 19-21 located around 386 and 406 nm.…”

“…Directed proton transfer was recognized to be essential for esterase‐like activity of BSA as well as for induction of phenoxyl radical . Furthermore, the cooperativeness means more polarized bonds and water dipoles resulting in higher nucleophilic potential of the latter, and the nucleophilic attack of water is involved in both the deacetylation of BSA on hydrolysis of p ‐NPA as well as in the removal of nitro group from p ‐NP . Bulk thermal effects of IR light can be excluded as monitored sample temperature was changing only by (0.4 ± 0.3)°C, which was way too low to measurably affect the reaction rates.…”

“…23 Furthermore, the cooperativeness means more polarized bonds and water dipoles resulting in higher nucleophilic potential of the latter, and the nucleophilic attack of water is involved in both the deacetylation of BSA on hydrolysis of p-NPA 1 as well as in the removal of nitro group from p-NP. 12 ; red-samples exposed to infrared radiation; blue-degassed samples; pink-samples exposed to infrared radiation after degassing step. Lines of the same color denote different experimental batches for the same experimental conditions comparable with those promoted by temperature increase from 25°C to 40°C in our experimental setup.…”

“…Anaerobic biological degradation or catalytic reduction (eg, with the use of nanoparticles) leads in general to formation of 4‐aminophenol . Aqueous photolysis of nitrophenols by solar ultraviolet (UV) radiation proceeding via radical formation results in release of nitro group in the form of nitrous acid …”

“…[9][10][11] Aqueous photolysis of nitrophenols by solar ultraviolet (UV) radiation proceeding via radical formation results in release of nitro group in the form of nitrous acid. 12 In this study, we explore the activity of BSA toward p-NPA to show new routes of this interaction going beyond usually considered hydrolysis step and including protein-supported transformation of p-NP. We also demonstrate the potential of the remote physical trigger-infrared radiation to affect those chemical transformations.…”