臭氧化降解水中硝基氯苯Ⅱ.产物和机理分析

为探讨臭氧与几种硝基氯苯的作用机理,利用GC-MS和LC-MS对水中对硝基氯苯(pCNB)、间硝基氯苯(mCNB)、邻硝基氯苯(oCNB)3种同分异构体的臭氧化过程进行研究.3种硝基氯苯的臭氧化产物主要包括氯酚、硝基酚、硝基氯酚等酚类物质和草酸、丙二酸、顺丁烯二酸、己二烯二酸等羧酸类物质.pCNB在臭氧化过程中,氯基和硝基可以被.OH取代,生成硝基酚和氯酚,而oCNB和mCNB的氧化产物中,未检出硝基酚和氯酚,3种硝基氯苯苯环上的氢均可被.OH取代,生成硝基氯酚,GC/LC-MS共检测出10种不同的硝基氯酚同分异构体.CNB苯环上的-Cl和-NO2的取代位不同,致使苯环上碳原子的电子云密度和自然轨道布居数(NOB)具有一定的差异,.OH与苯环上的H发生取代反应的几率与相应C的电子云密度和NOB具有一定的相关性,而与对应的键能关系不大,.OH与硝基氯苯的反应可能类似于芳环的亲电取代反应.

Ozonation degradation of nitrochiorobenzene isomers in aqueous solution: ii. products and mechanism

To study the mechanisms of degradation of chloronitrobenzenes in water by ozonation,the processes of ozonational degradation of p-nitrochlorobenzene(pCNB),m-nitrochlorobenzene(mCNB) and o-nitrochlorobenzene(oCNB) were investigated by means of GC-MS and LC-MS.The products of these three CNBs mainly contained phenolic matters such as chlorophenol,nitrophenol and nitrochlorophenol,as well as carboxylic matters such as oxalic acid and malonic acid,maleic acid,muconic acid.In the process of ozonation degradation of pCNB,-Cl and-NO2 could be replaced by·OH,meanwhile,chlorophenol and nitrophenol were formed.But in the processes of ozonation degradation of oCNB and mCNB,neither nitrophenol nor chlorophenol was detected.The hydrogen on the phenyl of all these three CNBs could be replaced by·OH,thus nitrochlorophenol was produced,and ten different nitrochlorophenols were detected by GC/LC-MS.The difference in the substitutional place of-Cl and-NO2 on the phenyl of CNB could lead to the difference of the electron cloud density of carbon and the natural bond orbital(NBO) population.The probability of the reaction between·OH and the hydrogen on the phenyl had a certain relationship with the electron cloud density of carbon and NOB,but had little relationship with the bond energy.The reaction between·OH and CNBs could be similar to the electrophilic substitution reactions of aryl.