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18The potential formation of nitrogenous disinfection by-products (N-DBPs) was investigated from the 19 chloramination of nitrogenous and non-nitrogenous aromatic compounds. All molecules led to the 20 formation of known N-DBPs (e.g., dichloroacetonitrile, dichloroacetamide) with various production 21 yields. Resorcinol, a major precursor of chloroform, also formed di-/tri-chloroacetonitrile, di-/tri-22 chloroacetamide, and haloacetic acids, indicating that it is a precursor of both N-DBPs and 23carbonaceous DBPs (C-DBPs) upon chloramination. More detailed experiments were conducted on 24 resorcinol to understand N-DBPs formation mechanisms and to identify reaction intermediates. Based 25 on the accurate mass from high resolution Quadrupole Time-of-Flight GC-MS (GC-QTOF) and 26 fragmentation patterns from electronic impact and positive chemical ionization modes, several 27 products were tentatively identified as nitrogenous heterocyclic compounds (e.g., 3-chloro-5-hydroxy-28 1H-pyrrole-2-one with dichloromethyl group, 3-chloro-2,5-pyrroledione). These products were 29 structurally similar to the heterocyclic compounds formed during chlorination, such as the highly 30 mutagenic MX (3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone) or halogenated pyrroles. To 31 our knowledge, this is the first time that the formation of halogenated nitrogenous heterocyclic 32 compounds is reported from chloramination process. The formation of these nitrogenous by-products 33 during chloramination might be of concern considering their potential toxicity. 34 ABSTRACT ART35 36 37 INTRODUCTION 38