Accordingly, UV-A irradiation of PAB leads to the instantaneous generation of bromine and phenacyl radicals through PAB's excited triplet state in high quantum yields, as previously demonstrated by Scaiano 67 and our group. Subsequent abstraction of methylene proton (-hydrogen abstraction) of 2-PAP by readily formed bromine radical and the abstraction of proton by phenacyl radical from possibly aqueous solvent led to the production of -carbon radical (2), HBr and acetophenone (1), respectively. Then, 2 couples with the bromine radical resulting in the chiral brominated product (3) which was confirmed by both 2D-HSQC NMR spectrum (Figure ) and LC-HRMS (Figure ). It was previously demonstrated, as discussed in the introduction part, that carbonyl-containing brominated aromatic compounds can homolytically cleave under UV irradiation provoking a scission reaction. In this case, slow disappearance of (3) was observed in 1 H NMR spectrum (Figure ), leading to acetophenone (1) and phenol (4) through β-O-4 cleavage of (2). Benzaldehyde (5) which should be the product of C-C bond cleavage of (2), was also identified both in H NMR (Figure , peaks at 10 ppm, 8.0 ppm, 7.5 ppm) and LC-HRMS (Figure ). A possible route for benzoic acid (8) observed in LC-HRMS might be the following: 1 reacts with atmospheric oxygen to form the peroxy radical (6). 6 subsequently abstracts protons from water molecules present in the solvent to generate hydroperoxide (7) which is attacked by H + (coming from HBr), and transformed to benzoic acid (8) and phenol (4). Initial pH = 4.9 dropped to a final pH = 3.4 at the end of the photocatalytic reaction confirming the HBr release. Darkening of the color of the photocatalyzed reaction can be attributed to the trace formation of coupling species (9 and compound with m/z = 370 g/mol) having extended conjugation, as previously encountered. Coupling was also supported by UV-vis spectroscopy where a slight red-shift to visible region in the spectrum was observable after the photoreaction (Figure ). Control experiment performed in the absence of PAB under identical reaction conditions did not show any change in 1 H NMR spectrum underlining the important role of PAB in the photocatalyzed cleavage reactions (Figure ).