Detecting Early-Stage Intermediates of Free-Radical Oxidative Degradation in Charged Aqueous Microdroplets

Abstract

We report the detection of early-stage intermediates of spontaneous free-radical oxidation of organic pollutants such as aliphatic amino alcohols and diamines in charged aqueous microdroplets in the ambient atmosphere. We propose that the intrinsic formation of reactive oxygen species at the air–water interface is responsible for the radical oxidation of the sp3 carbon. We suggest that our work will aid the understanding of the degradation mechanisms of organic molecules in the environment.

Spontaneous Oxidation in Aqueous Microdroplets: Water Radical Cation as Primary Oxidizing Agent

“…Table 1 summarizes the classification, reaction conditions, and oxidants suggested in various studies. Generally, two types of oxidation have been observed in microdroplets: (i) simple oxidation of substrates, where a single reactant is oxidized by an oxidant to yield the final product, [13,14,16,60,62–67] and (ii) oxidative coupling reactions, in which one reactant is oxidized to generate a radical species (as intermediate) that subsequently couples with another reactant to produce a coupling product [15,68–70] . As shown in table 1, spontaneous oxidation encompasses a wide array of compounds, from organic compounds (most cases), through inorganic compounds (reaction 1.6) to large biomolecules (reactions 1.12 and 1.13).…”

Spontaneous Oxidation in Aqueous Microdroplets: Water Radical Cation as Primary Oxidizing Agent

“…Table 1 summarizes the classification, reaction conditions, and oxidants suggested in various studies. Generally, two types of oxidation have been observed in microdroplets: (i) simple oxidation of substrates, where a single reactant is oxidized by an oxidant to yield the final product, [13,14,16,60,[62][63][64][65][66][67] and (ii) oxidative coupling reactions, in which one reactant is oxidized to generate a radical species (as intermediate) that subsequently couples with another reactant to produce a coupling product. [15,[68][69][70] As shown in table 1, spontaneous oxidation encompasses a wide array of compounds, from organic compounds (most cases), through inorganic compounds (reaction 1.6) to large biomolecules (reactions 1.12 and 1.13).…”