Halogen substitution reactions of halobenzenes during water disinfection

Transformation of Organic Compounds during Water Chlorination/Bromination: Formation Pathways for Disinfection By-Products (A Review)

“…In our laboratory, a model study of the substitution of iodine and bromine for chlorine in the simplest aromatic substrates with activating substituents (OH, OCH 3 , and NH 2 ) was carried out under conditions of aqueous chlorination with sodium hypochlorite. Detenchuk et al [ 53 ] found that, in the case of organoiodine compounds, ipso substitution is the dominant process if the halogen is in the ortho - or para -position to the activating substituent. For example, in the case of 4-iodoanisole, the fraction of the corresponding 4‑chloroanisole is higher than 75% of all reaction products.…”

“…The replacement of bromine with chlorine is not so active, but such products are present in the reaction mixture. Moreover, due to its high activity [ 49 ] and slower oxidation to the bromate anion, the eliminated Br + cation can attack aromatic substrates in the reaction mixture to form, for example, polybrominated products [ 53 ]. Due to the activity of Br + , bromine can also displace chlorine from activated aromatic substrates under aqueous bromination conditions, although the yields of such reactions are very low.…”

“…Longterm observations of the Ufa water treatment station clearly demonstrated that the fraction of bromine in semivolatile DBPs (four to six carbon atoms) is greater than that of chlorine, whereas the fraction of chlorine in volatile DBPs is much higher [50]. In addition, bromine is easily eliminated from aromatic substrates under conditions of aqueous chlorination or chloramination, being replaced by chlorine as a result of electrophilic aromatic substitution according to the ipso mechanism [51][52][53].…”

“…H( 1 aqueous chlorination with sodium hypochlorite. Detenchuk et al [53] found that, in the case of organoiodine compounds, ipso substitution is the dominant process if the halogen is in the ortho-or para-position to the activating substituent. For example, in the case of 4-iodoanisole, the fraction of the corresponding 4-chloroanisole is higher than 75% of all reaction products.…”

“…The range and levels of reaction products significantly depend on the experimental conditions. Although organoiodine compounds are easily transformed under conditions of aqueous chlorination with the substitution of iodine for chlorine [51][52][53]107], two organoiodine products were detected in experiments with the addition of iodide anions [135]. Iron ions and iodides accelerate the chlorination reaction, and the presence of copper ions under bromination conditions leads to an almost 100-fold increase in the yield of bromoform [135,136].…”