The photochemical production of hydroxylating species (e.g., hydroxyl radical (OH)) from dissolved organic matter (DOM) has been well documented. Quantum yields for the production of these species have been quantified in previous studies and are in the order of 10<sup>-5</sup> – 10<sup>-4</sup> depending on the source of the organic matter. These quantum yields are, partially, independent of photo-Fenton chemistry, and represent hydrogen-peroxide independent production of these species. It has been shown that lower energy hydroxylating species, in addition to free OH, are present upon the photolysis of DOM. The source of these lower energy hydroxylating species has been attributed, in part, to the presence of quinones in DOM. This study explores the DOM structural moieties responsible for its hydroxylating capacity in two ways. First, by testing the ability of various DOM model sensitizers to photohydroxylate commonly used probe compounds and then by exploring the ability of methanol to quench free OH in comparison to other species thought to be lower energy hydroxylators. The main classes of sensitizers tested were aromatic ketones, quinones, and hydroxybenzoic acids, which were selected to cover a range of molecular structures, triplet state one electron reduction potentials, and triplet energies. Results indicate that only quinones and hydroxybenzoic acids have the capacity to hydroxylate OH probe compounds when photolyzed, with quinones having the highest quantum yields.

Investigation of the production of hydroxylating species from DOM model sensitizers

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.