Formation and Reactions of Chloramines

Phenol reacts with monochloramine at neutral pH in a multi-step reaction to form a colored compound, indophenol blue (42 AWWA, 1989). The sequence of its formation appears to be initiated by amination at thep-position of phenol, followed by oxidation of 4-aminophenol to an iminoquinone and condensation to form the ultimate product (Equation 5.20). The reaction is used in a standard procedure for the determination of ammonia in natural waters. Amination reactions of a few other compounds by NH2CI have been observed under some conditions (for example, phenolic ethers are converted to aniline derivatives in methanol Kovacic et al., 1970), but it is uncertain to what extent these would occur under environmental conditions. 

Aromatic amines, which are far less basic than the aliphatic forms, tend to react by substitution on the ring rather than by N-chlorination the amino group is a powerful electron donor (cf. Chapter 1). Thus, aniline gives rise to /7-chloroaniline as the principal product of reaction with HOCl (Barnhart and Campbell, 1972 Hwang et al., 1990). However, benzidine (43) reacts rapidly with HOCl to form a deeply colored polymer without ring chlorine substitution. It was suggested that an oxidized polymer similar to the common dye, aniline black (44) had been produced (Jenkins et al., 1978). 

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