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最近发现卤代醌能通过不依赖于金属离子的途径促进氢过氧化物的分解而产生羟基或烷氧自由基,并认为该反应通过亲核取代形成醌-过氧化物中间产物,随后均裂分解生成羟基或烷氧自由基和醌氧自由基中间体.然而,在先前的研究中,无论是对其主要反应产物,还是对该机制中提出的醌-过氧化物中间体和醌氧自由基,都没有被完全分离鉴定.在最新的研究中,以2,5-二氯-1,4-苯醌(DCBQ)与叔丁基过氧化氢(t-BuOOH)反应体系为研究对象,通过半制备高效液相色谱(HPLC),分离纯化出一种主要反应产物,采用多种分析方法鉴定该产物为2-羟基-3-叔丁氧基-5-氯-1,4-苯醌(CBQ(OH)-O-t-Bu),原来该物质是先前假设的醌-过氧化物中间体(CBQ-OO-t-Bu)的重排异构体.继而发现,自旋捕获剂DMPO(5,5-二甲基-1-吡咯啉-N-氧化物)能抑制CBQ(OH)-O-t-Bu的形成,同时伴随着形成一种新的含有一个氯原子、质荷比m/z为268的DMPO加合物.在此基础上,综合采用电子自旋共振、核磁共振-氢谱、高效液相-傅里叶变换离子回旋共振等分析方法,并使用O-17标记的H2O2的研究表明:DMPO捕获的并不是以氧为中心的醌氧自由基(CBQ-O),而是其共振异构体——一种以碳为中心的醌酮自由基(CBQ=O).这是第一次检测到一种新型的以碳为中心的醌酮自由基,为先前提出的卤代醌介导的不依赖金属离子的氢过氧化物的分解机制提供了直接的实验证据,并丰富和完善了该机制.
It has recently been found that haloquinones can generate hydroxyl or alkoxy radicals by promoting the decomposition of hydroperoxides via a metal ion-independent route and that the reaction is believed to form quinone-peroxide intermediates by nucleophilic substitution followed by cleavage However, in previous studies, both for its main reaction products, and for the quinone-peroxide intermediates proposed in this mechanism and the quinone-oxygen free radical Are not completely separated and identified.In the latest research, the reaction system of 2,5-dichloro-1,4-benzoquinone (DCBQ) and tert-butyl hydroperoxide (t-BuOOH) A major reaction product was isolated and purified by semi-preparative high performance liquid chromatography (HPLC). The product was identified as 2-hydroxy-3-tert-butoxy-5-chloro-1,4-benzoquinone (CBQ (OH) -Ot-Bu), which was originally a rearranged isomer of the previously assumed quinone-peroxide intermediate (CBQ-OO-t-Bu) .Then it was found that the spin-trapping agent DMPO 5-dimethyl-1-pyrroline-N-oxide) inhibits the formation of CBQ (OH) -Ot-Bu, accompanied by the formation of a new compound containing a chlorine atom with a mass- for 268 DMPO adduct.On the basis of the above, we use the method of electron spin resonance, nuclear magnetic resonance-hydrogen spectrum, high-performance liquid phase-Fourier transform ion cyclotron resonance and so on, and study the O-17 labeled H2O2 Showed that DMPO did not capture the quinone oxygen radical (CBQ-O) that is centered on oxygen, but rather its resonance isomer, a carbon-centered quinone ketone radical (CBQ = O) For the first time, a new carbon-centered quinone-based free radical was detected, providing direct experimental evidence for the previously proposed haloquinone-mediated decomposition mechanism of metal ion-free hydroperoxides and for enrichment And improve the mechanism.