Products and pathways of 2-bromophenol oxidation by potassium permanganate

The purpose of this article was to investigate the mechanism responsible for the formation of brominated polymeric products from oxidation of bromophenols by aqueous potassium permanganate. Experiments were conducted to determine brominated oxidation products of 2-bromophenol by aqueous potassium permanganate using liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS). The results showed that four polymeric products of m/z 341/343 (at m/z 79) and 343/345 (at m/z 81) containing two bromine atoms were detected by the precursor ion scan (PIS) approach at m/z 79 and 81, respectively, and their abundance was about 1:1, consistent with the natural isotope of bromine atom. The four polymeric products were isomers, and they were formed by the C-O and C-C coupling of 2-bromophenoxy radicals, where the C-C coupling products eluted faster than the C-O coupling ones in LC-MS/MS. According to phenolic coupling theory, there would be eight brominated polymeric products. However, they were partially detected, probably due to the difference in coupling rates of phenoxy radicals.