Reactions of chlorine with inorganic and organic compounds during water treatment—Kinetics and mechanisms: A critical review

Kinetic models and pathways of ronidazole degradation by chlorination, UV irradiation and UV/chlorine processes.

Aqueous chlorination of carbamazepine: Kinetic study and transformation product identification

This paper is a critical review of current knowledge of organic chloramines in water systems, including their formation, stability, toxicity, analytical methods for detection, and their impact on drinking water treatment and quality The term organic chloramines may refer to any halogenated organic compounds measured as part of combined chlorine (the difference between the measured free and total chlorine concentrations), and may include N-chloramines, N-chloramino acids, N-chloraldimines and N-chloramides Organic chloramines can form when dissolved organic nitrogen or dissolved organic carbon react with either free chlorine or inorganic chloramines They are potentially harmful to humans and may exist as an intermediate for other disinfection by-products However, little information is available on the formation or occurrence of organic chloramines in water due to a number of challenges One of the biggest challenges for the identification and quantification of organic chloramines in water systems is the lack of appropriate analytical methods In addition, many of the organic chloramines that form during disinfection are unstable, which results in difficulties in sampling and detection To date research has focussed on the study of organic monochloramines However, given that breakpoint chlorination is commonly undertaken in water treatment systems, the formation of organic dichloramines should also be considered Organic chloramines can be formed from many different precursors and pathways Therefore, studying the occurrence of their precursors in water systems would enable better prediction and management of their formation

Organic chloramines in chlorine-based disinfected water systems: A critical review.

Industrial and transport accidents, accidental releases during recreational swimming pool water treatment, household accidents due to mixing bleach with acidic cleaners, and, in recent years, usage of chlorine during war and in acts of terror, all contribute to the general and elevated state of alert with regard to chlorine gas. We here describe chemical and physical properties of Cl2 that are relevant to its chemical reactivity with biological molecules, including water-soluble small-molecular-weight antioxidants, amino acid residues in proteins, and amino-phospholipids such as phosphatidylethanolamine and phosphatidylserine that are present in the lining fluid layers covering the airways and alveolar spaces. We further conduct a Cl2 penetration analysis to assess how far Cl2 can penetrate the surface of the lung before it reacts with water or biological substrate molecules. Our results strongly suggest that Cl2 will predominantly react directly with biological molecules in the lung epithelial lining fluid, such as low-molecular-weight antioxidants, and that the hydrolysis of Cl2 to HOCl (and HCl) can be important only when these biological molecules have been depleted by direct chemical reaction with Cl2. The results from this theoretical analysis are then used for the assessment of the potential benefits of adjuvant antioxidant therapy in the mitigation of lung injury due to inhalation of Cl2 and are compared with recent experimental results.

Elucidating mechanisms of chlorine toxicity: reaction kinetics, thermodynamics, and physiological implications

Various secondary amides have been N-chlorinated, at high and at low pH. The reactivity of the chlorinating reagents with all the amides investigated was found to have the sequenceThe substituent groups R1 and R2 of the amide were found to have large effects on the rate of chlorination. With the three molecular chlorinating agents, the reactivity of the amides was found to be in the orderWith hypochlorite ion the reverse order of reactivity was observed. These results are discussed and reaction mechanisms proposed. It is proposed that, when a hypochlorite ion is a chlorinating agent, the primary reaction is hydrogen bond formation between the amido hydrogen and the hypochlorite oxygen atom, but that the donation of electrons from the amido N to the Cl atom is the primary reaction with the molecular chlorinating agents.

M. Wayman

Papers

N-Chlorination of secondary amides. II. Effects of substituents on rates of N-chlorination