水自由基阳离子与苯及其衍生物反应的质谱研究  

Study on Reaction of Water Dimer Radical Cation with Benzene and its Derivatives Using Mass Spectrometry

作　　者：杨黄丽 高校飞 谭国斌 张兴磊[2] 周振 陈焕文[2,4] YANG Huang-li;GAO Xiao-fei;TAN Guo-bin;ZHANG Xing-lei;ZHOU Zhen;CHEN Huan-wen(Institute of Mass Spectrometry and Atmospheric Environment,Jinan University,Guangzhou 510630,China;Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation,East China University of Technology,Nanchang 330013,China;Guangzhou Hexin Instrument Co.,Ltd,Guangzhou 510530,China;Mass Spectrometry Laboratory for BioSample Analysis,Jiangxi University of Chinese Medicine,Nanchang 330004,China)

机构地区：[1]暨南大学,质谱仪器与大气环境研究所,广东广州510630 [2]东华理工大学,江西省质谱科学与仪器重点实验室,江西南昌330013 [3]广州禾信仪器股份有限公司,广东广州510530 [4]江西中医药大学,生命样品直接质谱分析研究室,江西南昌330004

出　　处：《质谱学报》2024年第4期482-491,I0002,共11页Journal of Chinese Mass Spectrometry Society

基　　金：国家自然科学基金(22204017);江西省自然科学基金(20232BAB203022);江西中医药大学校级科技创新团队发展项目(CXTD22005)。

摘　　要：研究水自由基阳离子的化学性质对阐释水相化学反应机理有着重要意义。本文研究了在线制备的(H_(2)O)_(2)^(+·)(m/z 36)与苯及其衍生物反应的特点。结果表明,当(H_(2)O)_(2)^(+·)与苯(C_(6)H_(6))、苯甲醚(C_(7)H_(8)O)、2,4-二甲基苯胺(C_(8)H_(11)N)等没有吸电子基团的化合物反应时,除产生对应的电子转移反应产物(C_(6)H_(6))^(+·)(m/z 78)、(C_(7)H_(8)O)^(+·)(m/z108)或质子转移反应产物(C_(8)H_(11)N+H)+(m/z 122)外,还发现苯酚相关产物(C_(6)H_(5)OH)^(+·)(m/z 94)、(C_(7)H_(7)O-OH)^(+·)(m/z 124)以及(C_(8)H_(10)NOH+H)+(m/z 138)。同位素标记实验表明,苯酚相关产物中的OH来源于水自由基阳离子。然而,当(H_(2)O)_(2)^(+·)与苯甲腈(C_(6)H_(5)CN)或硝基苯(C_(6)H_(5)NO_(2))等有强吸电子基团的取代苯反应时,主要通过取代反应产生(C_(6)H_(5)CN+H_(2)O)^(+·)(m/z 121)和(C_(6)H_(5)NO_(2)+H_(2)O)^(+·)(m/z 141),并未发现羟基化产物。由以上结果可知,(H_(2)O)_(2)^(+·)与底物分子的反应可通过电子转移(底物自由基阳离子)、质子转移(质子化产物)、解离电子转移(羟基化产物)和取代等4个过程发生,这可能与(H_(2)O)_(2)^(+·)存在(H_(2)O)H^(+)-^(·)OH和[H_(2)O∴OH_(2)]^(+·)_(2)种互变结构有关。本研究推测,苯环上的吸电子基团有利于[H_(2)O∴OH_(2)]^(+·)结构的存在,从而发生取代反应,当苯环上没有吸电子基团时,苯环上的富电子体系有利于(H_(2)O)H^(+)-^(·)OH结构的存在,而质子转移结构中的羟基自由基可以将苯氧化成苯酚,该结果有助于阐明苯及其衍生物与(H_(2)O)_(2)^(+·)相关的化学反应过程。Study of chemical properties of water radical cations is of great significance for elucidating related reactions process.In this paper,the reaction characteristics of(H_(2)O)_(2)^(+·)prepared online with several benzene derivatives were investigated.The results showed that,when(H_(2)O)_(2)^(+·)reacted with aromatic compounds without electron-withdrawing groups,such as benzene(C_(6)H_(6),78 u),anisole(C_(7)H_(8)O,108 u)and 2,4-dimethylaniline(C_(8)H_(11)N,121 u),the corresponding phenol product((C_(6)H_(5)OH)^(+·),m/z 94),(C_(7)H_(7)O−OH)^(+·),m/z 124)and(C_(8)H_(10)NOH+H)+,m/z 138))were observed,accompanied with the production of electron transfer(ET)products(C_(6)H_(6))^(+·),(C_(7)H_(8)O)^(+·))or proton transfer(PT)product((C_(8)H_(11)N+H)+).Isotope labeling experiments proved that OH in corresponding phenol products was originated from(H_(2)O)_(2)^(+·).Interestingly,when(H_(2)O)_(2)^(+·)reacted with substituted benzenes bearing strong electron-withdrawing group,such as benzonitrile(C_(6)H_(5)CN,103 u)and nitrobenzene(C_(6)H_(5)NO_(2),123 u),the main products were the radical substituted adducts(C_(6)H_(5)CN+H_(2)O)^(+·)(m/z 121)and(C_(6)H_(5)NO_(2)+H_(2)O)^(+·)(m/z 141),respectively,without phenol products or substituted benzene radical cation were noticed.It was obvious that the reaction between(H_(2)O)_(2)^(+·)and the substrate occurred through four competing processes:(a)electron transfer(ET)reaction,in which aromatic compounds release an electron to(H_(2)O)_(2)^(+·)to from an aromatic radical cation;(b)proton transfer(PT)reaction in which aromatic compounds got a proton derived from the dissociation of(H_(2)O)_(2)^(+·);(c)dissociative electron transfer(DET)reaction,accompanied with the electron transfer process,C−H bond cleavage and C−OH bond formation;(d)radical substitution reaction in which a radical cation adduct consisting of aromatic molecule and H_(2)O generates.It was speculated that the diverse reactivity of(H_(2)O)_(2)^(+·)was owe to its two interchange structures((H_(2)O)H^(+)

关 键 词：水自由基阳离子 苯及其衍生物 质子转移结构 两中心三电子结构 质谱 

分 类 号：O657.63[理学—分析化学]