A computational study of site-selective hydrogen abstraction by sulfate radical anion

Beyond the formation: unveiling the atmospheric transformation of organosulfates via heterogeneous OH oxidation

Organosulfates (OSs), characterized with a sulfate ester group (R-OSO3-), are abundant constituents in secondary organic aerosols. Recent laboratory-based investigations have revealed that OSs can undergo efficient chemical transformation through heterogeneous oxidation by hydroxyl radicals (˙OH, interchangeably termed as OH in this article), which freshly derives functionalized and fragmented OSs. The reaction not only contributes to the presence of structurally transformed OSs in the atmosphere of which sources were unidentified, but it also leads to the formation of inorganic sulfates (e.g., SO42-) with profound implication on the form of aerosol sulfur. In this article, we review the current state of knowledge regarding the heterogeneous OH oxidation of OSs based on state-of-the-art designs of experiments, computational approaches, and chemical analytical techniques. Here, we discuss the formation potential of new OSs and SO42-, in light of the influence of diverse OS structures on the relative importance of different reaction pathways. We propose future research directions to advance our mechanistic understanding of these reactions, taking into account aerosol matrix effects, interactions with other atmospheric pollutants, and the incorporation of experimental findings into atmospheric chemical transport models.

Direct Photocatalyzed Hydrogen Atom Transfer (HAT) for Aliphatic C-H Bonds Elaboration

Direct photocatalyzed hydrogen atom transfer (d-HAT) can be considered a method of choice for the elaboration of aliphatic C–H bonds. In this manifold, a photocatalyst (PC_HAT) exploits the energy of a photon to trigger the homolytic cleavage of such bonds in organic compounds. Selective C–H bond elaboration may be achieved by a judicious choice of the hydrogen abstractor (key parameters are the electronic character and the molecular structure), as well as reaction additives. Different are the classes of PCs_HAT available, including aromatic ketones, xanthene dyes (Eosin Y), polyoxometalates, uranyl salts, a metal-oxo porphyrin and a tris(amino)cyclopropenium radical dication. The processes (mainly C–C bond formation) are in most cases carried out under mild conditions with the help of visible light. The aim of this review is to offer a comprehensive survey of the synthetic applications of photocatalyzed d-HAT.