Halogenation\nof Anilines: Formation of Haloacetonitriles\nand Large-Molecule Disinfection Byproducts

Aniline-related structures are common\nin anthropogenic chemicals,\nsuch as pharmaceuticals and pesticides. Compared with the widely studied\nphenolic compounds, anilines have received far less assessment of\ntheir disinfection byproduct (DBP) formation potential, even though\nanilines and phenols likely exhibit similar reactivities on their\nrespective aromatic rings. In this study, a suite of 19 aniline compounds\nwith varying <i>N</i>- and ring-substitutions were evaluated\nfor their formation potentials of haloacetonitriles and trihalomethanes\nunder free chlorination and free bromination conditions. Eight of\nthe aniline compounds formed dichloroacetonitrile at yields above\n0.50%; the highest yields were observed for 4-nitroaniline, 3-chloroaniline,\nand 4-(methylsulfonyl)aniline (1.6–2.3%). Free bromination\ngenerally resulted in greater haloacetonitrile yields with the highest\nyield observed for 2-ethylaniline (6.5%). The trihalomethane yields\nof anilines correlated with their haloacetonitrile yields. Product\nanalysis of aniline chlorination by liquid chromatography–high-resolution\nmass spectrometry revealed several large-molecule DBPs, including\nchloroanilines, (chloro)hydroxyanilines, (chloro)benzoquinone imines,\nand ring-cleavage products. The product time profiles suggested that\nthe reaction pathways include initial ring chlorination and hydroxylation,\nfollowed by the formation of benzoquinone imines that eventually led\nto ring cleavage. This work revealed the potential of aniline-related\nmoieties in micropollutants as potent precursors to haloacetonitriles\nand other emerging large-molecule DBPs with the expected toxicity.