Formation of nitrogen-containing disinfection by-products induced by amide moiety in dissolved organic matter

Aqueous chlorination may produce numerous nitrogenous disinfection by-products (N-DBPs), which are a significant toxicological concern. While the transformations of amines are well studied, the DBP formation pathways induced by the amide moieties remain poorly characterized. Presence of any alkyl group at nitrogen significantly complicates any transformation, revealing the absence of N-dealkylation for amides under aqueous chlorination. Instead, the amide group's influence on DBP formation is primarily mediated by its ability to undergo keto-enol tautomerization, leading to more reactive enolic forms. However, substantial DBP generation from amides necessitates high active chlorine concentrations and prolonged reaction times. For N,N-disubstituted amides, DBP formation largely relies on the presence of additional reactive functionalities like CC double bonds or aromatic rings. Mono N-substituted amides exhibited limited reactivity, primarily yielding N-Cl derivatives.