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首页> 外文期刊>Environmental Science & Technology >Oxidation of Flame Retardant Tetrabromobisphenol A by Singlet Oxygen
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Oxidation of Flame Retardant Tetrabromobisphenol A by Singlet Oxygen

机译：单线态氧氧化阻燃四溴双酚A

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Wide use of flame retardants can pose an environmental hazard, and it is of interest to investigate how they may degrade. We report here that 3,3',5,5'-tetrabromobisphenol A (TBBPA) is subject to photosensitized oxidation involving singlet molecular oxygen (~1O_2). By using visible light and rose bengal or methylene blue as ~1O_2 photosensitizers, we have found that TBBPA is a ~1O_2 quencher. The quenching rate constant, k_q, depends on TBBPA ionization (pK= 7.4). In acetonitrile, where TBBPA is undissociated, the k_q value is 6.1 × 10~5 M~(-1) s~(-1) for a TBBPA monomer and decreases to 2.9 × 10~4 M_(-1) s~(-1) for TBBPA dimers and/or aggregates. TBBPA dissociates in aqueous solutions, and its k_ q value is 1.44 × 10~9 M~(-1) s~(-1) in alkaline solution, decreasing to 3.9 × 10~8 M~(-1) s~(-1) at pH 7.2. The strong ~1O_2 quenching by TBBPA anion initiates an efficient oxidation of TBBPA, which results in oxygen consumption in aqueous micellar (e.g., Triton X-100) solutions containing photosensitizer. This oxygen consumption is mediated by transient radical species, which we detected by using EPR spectroscopy. We observed two major radicals and one minor radical generated from TBBPA by reaction with ~1O_2 at pH 10. One was identified asthe 2,6-dibromo-p.-benzosemiquinone radical (a_(2H) = 2.36 G, g = 2.0056). A second radical (a_H = 2.10 G, g = 2.0055) could not be identified but was probably a 2,6-dibromo-p-benzosemiquinone radical containing an EPR-silent substituent at the 3-position. Spin trapping with 5,5-dimethyl-1-pyrroline N-oxide (DPMO) showed that other minor radicals (hydroxyl, carbon-centered) are also generated during the reaction of TBBPA with ~1O_2. The photosensitized production of radicals and oxygen consumption were completely inhibited by the azide anion, an efficient physical ~1O_2 quencher. Because TBBPA is a stable compound that at neutral pH does not absorb much of the atmosphere-filtered solar radiation, its photosensitized oxidation by ~1O_2 may be the key reaction initiating or mediating TBBPA degradation in the natural environment
机译：阻燃剂的广泛使用会造成环境危害，因此研究它们如何降解会引起人们的兴趣。我们在这里报告3,3'，5,5'-四溴双酚A（TBBPA）受到涉及单线态分子氧（〜1O_2）的光敏氧化作用。通过使用可见光和玫瑰红或美蓝作为〜1O_2光敏剂，我们发现TBBPA是〜1O_2淬灭剂。猝灭速率常数k_q取决于TBBPA电离（pK = 7.4）。在未分离TBBPA的乙​​腈中，TBBPA单体的k_q值为6.1×10〜5 M〜（-1）s〜（-1），降低到2.9×10〜4 M _（-1）s〜（- 1）用于TBBPA二聚体和/或聚集体。 TBBPA在水溶液中解离，在碱性溶液中其k_ q值为1.44×10〜9 M〜（-1）s〜（-1），降至3.9×10〜8 M〜（-1）s〜（- 1）在pH 7.2下。用TBBPA阴离子强烈的〜1O_2淬灭引发了TBBPA的有效氧化，这导致了含有光敏剂的胶束水溶液（例如Triton X-100）中的氧气消耗。这种耗氧量是由瞬态自由基物种介导的，我们使用EPR光谱仪检测到了这些自由基。我们观察到在pH 10下与〜1O_2反应，TBBPA产生了两个主要自由基，一个次要自由基被鉴定为2,6-二溴-对-苯并半醌自由基（a_（2H）= 2.36 G，g = 2.0056）。第二个基团（a_H = 2.10 G，g = 2.0055）无法确定，但可能是一个在3位含有EPR沉默取代基的2,6-二溴对苯并半醌基团。用5,5-二甲基-1-吡咯啉N-氧化物（DPMO）进行自旋捕集表明，在TBBPA与〜1O_2反应期间还产生了其他次要自由基（以碳为中心的羟基）。叠氮化物阴离子（一种有效的物理〜1O_2猝灭剂）完全抑制了自由基的光敏生成和耗氧量。由于TBBPA是一种稳定的化合物，在中性pH值下不会吸收大部分被大气过滤的太阳辐射，因此〜1O_2对它的光敏氧化可能是在自然环境中引发或介导TBBPA降解的关键反应

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