KMnO_4降解2-溴酚的氧化产物与反应路径

Products and pathways of 2-bromophenol oxidation by potassium permanganate

为了探讨KMnO_4氧化降解溴酚过程中溴代聚合产物的生成机理,利用三重四级杆串联线性离子阱液相-质谱联用仪(LC-MS/MS)对KMnO_4氧化降解2-溴酚的产物进行检测分析.结果表明,根据溴的天然同位素特性,建立了LC-MS/MS-PIS(m/z 79和81)子找母质谱扫描方法测定溴代有机物,测得KMnO_4氧化降解2-溴酚的主要产物为4个质量数相同,341/343(m/z 79)和343/345(m/z 81),且分子结构中含有2个溴的氧化耦合产物,同位素丰度比为1:1.推测4个溴代聚合产物为同分异构体,由2-溴酚氧自由基通过C-C和C-O耦合产生,其中,C-C耦合的聚合产物先出峰,C-O耦合的聚合产物后出峰.2-溴酚氧自由基发生氧化耦合反应,理论上产生的8个溴代聚合产物并没有全部被检测到,主要是由于酚氧自由基的氧化耦合速率不同,导致聚合产物的形成产率不同.

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.