Halobenzoquinones are a group of disinfection byproducts formed by chlorination of certain substances in water. However, to date, the identities of halobenzoquinone precursors remain unknown. In this study, the formation… Click to show full abstract
Halobenzoquinones are a group of disinfection byproducts formed by chlorination of certain substances in water. However, to date, the identities of halobenzoquinone precursors remain unknown. In this study, the formation of 2,6-dichloro-1,4-benzoquinone (DCBQ), a typical halobenzoquinone, from 31 aromatic compounds was investigated after 60 min of chlorination. DCBQ was formed from 21 compounds at molar formation yields ranging from 0.0008% to 4.9%. Phenol and chlorinated phenols served as DCBQ precursors, as reported previously. Notably, DCBQ was also formed from para-substituted phenolic compounds. Compounds with alkyl and carboxyl groups as para-substituents led to relatively higher molar formation yields of DCBQ. Moreover, p-quinone-4-chloroimide, 2,6-dichloroquinone-4-chloroimide (2,6-DCQC), and para-substituted aromatic amines (e.g., aniline and N-methyl aniline) served as DCBQ precursors upon chlorination. It was deduced that DCBQ was formed from the para-substituted aromatic amines via 3,5-dichloroquinone-4-chloroimide, a structural isomer of 2,6-DCQC. These results suggested that DCBQ was formed by chlorination of natural organic matter containing para-substituted phenolic species and para-substituted aromatic amines, despite the absence of phenol in water.
               
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