Monochloramine

Monochloramine is oxidized slightly faster than ammonia (40). Monohromamine reacts much faster, k = 4Q (39). By contrast, dichloramine and dibromamine both react slower than m on oh a1 amines their k values are 1.3 and 20, respectively. 

A number of perhalides aie known, and one of the most stable is ammonium tetiachloioiodide [19702 3-3] NH IQ. Ammonia reacts with chlorine in dilute solution to give chloramines, a reaction important in water purification (see Cm,ORAMINES AND BROMAMINEs). Depending upon the pH of the water, either monochloramine [10599-90-3] NH2CI, or dichloramine [3400-09-7] NHCI2, is formed. In the dilutions encountered in waterworks practice, monochloramine is neady always found, except in the case of very acidic water (see Bleaching AGENTS Water). 

SuperchlorinationShock Treatment. Superchlorination or shock treatment of pool water is necessary since accumulation of organic matter, nitrogen compounds, and algae consumes free available chlorine and impedes disinfection. Reaction of chlorine with constituents of urine or perspiration (primarily NH" 4, amino acids, creatinine, uric acid, etc) produces chloramines (N—Cl compounds) which are poor disinfectants because they do not hydrolyze significantly to HOCl (19). For example, monochloramine (NH2CI) is only 1/280 as effective as HOCl against E. coli (20). 

In reahty the chemistry of breakpoint chlorination is much more complex and has been modeled by computer (21). Conversion of NH/ to monochloramine is rapid and causes an essentially linear increase in CAC with chlorine dosage. Further addition of chlorine results in formation of unstable dichloramine which decomposes to N2 thereby causing a reduction in CAC (22). At breakpoint, the process is essentially complete, and further addition of chlorine causes an equivalent linear increase in free available chlorine. Small concentrations of combined chlorine remaining beyond breakpoint are due primarily to organic chloramines. Breakpoint occurs slightly above the theoretical C1 N ratio (1.75 vs 1.5) because of competitive oxidation of NH/ to nitrate ion. Organic matter consumes chlorine and its oxidation also increases the breakpoint chlorine demand. Cyanuric acid does not interfere with breakpoint chlorination (23). 

The total concentration or amount of chlorine-based oxidants is often expressed as available chorine or less frequendy as active chlorine. Available chlorine is the equivalent concentration or amount of Cl needed to make the oxidant according to equations 1—4. Active chlorine is the equivalent concentration or amount of Cl atoms that can accept two electrons. This is a convention, not a description of the reaction mechanism of the oxidant. Because Cl only accepts two electrons as does HOCl and monochloramines, it only has one active Cl atom according to the definition. Thus the active chlorine is always one-half of the available chlorine. The available chlorine is usually measured by iodomettic titration (7,8). The weight of available chlorine can also be calculated by equation 5. 

Some nitrate is also formed, thus the HOCl/NH stoichiometry is greater than theoretical, ie, - 1.7. This reaction, commonly called breakpoint chlorination, involves intermediate formation of unstable dichloramine and has been modeled kinetically (28). Hypobromous acid also oxidizes ammonia via the breakpoint reaction (29). The reaction is virtually quantitative in the presence of excess HOBr. In the case of chlorine, Htde or no decomposition of NH occurs until essentially complete conversion to monochloramine. In contrast, oxidation of NH commences immediately with HOBr because equihbrium concentrations of NH2Br and NHBr2 are formed initially. As a result, the typical hump in the breakpoint curve is much lower than in the case of chlorine. 

The chemistry of NH2CI involves chlorination, amination, addition, condensation, redox, acid—base, and decomposition reactions. Monochloramine... 

Monochloramine is also used in organic synthesis for preparation of amines, substituted hydrazines, etc. For example, reaction of NH2CI with 3-azabicyclo [3.3.0]octane [5661-03-0] yields A/-amino-3-azabicyclo[3.3.0]octane [54528-00-6] a pharmaceutical intermediate (38). 

The estimated 1990 worldwide consumption of monochloramine for hydra2iae manufacture was 55,000 t. Consumption data on use of monochloramine ia water treatmeat are aot available. The U.S. consumption of chloroisocyanurates and halogenated hydantoias ia 1986 was 44,045 and 3,409 t, respectively (183). Consumption of tetrachloroglycolutil and other specialty /V-ha1amines, eg, trichioromelamine, is small. 

Hypochlorous acid reacts very rapidly and quantitatively with a slight excess of free ammonia forming monochloramine, NH2CI, which reacts at a slower rate with additional HOCl forming dichloramine, NHCI2. Trichloramine is formed when three moles of HOCl are added per mole of ammonia between pH 3—4 (100). Hypochlorous acid in the form of chlorine or hypochlorite is used in water treatments to oxidize ammonia by the process of break-point chlorination, which is based on formation of unstable dichloramine. The instabiHty of NHCI2 is caused by presence of HOCl and NCl (101,102). The reaction is most rapid at a pH of about 7.5 (103). Other nitrogen compounds such as urea, creatinine, and amino acids are also oxidized by hypochlorous acid, but at slower rates. Unstable iV-chloro compounds are intermediates in deammination of amino acids (104,105). 

Interaction of EMT with chlorine and monochloramine has been studied. Electronic spectra of EMT and of its product of oxidation by chlorine and monochloramines have been obtained. X = 470 nm for EMT, 400 nm and... 

The effect of pH alone on chlorine efficiency is shown in Figure 3. Chlorine exists predominantly as HOCl at low PH levels. Between pH of 6.0 and 8.5, a dramatic change from undissociated to completely dissociated hypochlorous acid occurs. Above pH 7.5, hypochlorite ions prevail while above 9.5, chlorine exists almost entirely as OCl. Increased pH also diminishes the disinfecting efficiency of monochloramine. 

Chloramine (Chloramide, Monochloramine), C1NH2, mw 51.48, N 27.2% a colorl liq or ciysts, mp -66°, decomps above the mp (Refs 2 8). It has an IR absorption peak at 2430A which can be used for spec trophotome trie analysis (Ref 3). It is unstable at room temp except in aq soln, so it is stored and handled in this form (Ref 4) CA Registry No 10599-90-3... 

Cromeans, T. L., Kahler, A. M., and Hill, V. R. (2010). Inactivation of adenoviruses, enteroviruses, and murine norovirus in water by free chlorine and monochloramine. Appl. Environ. Microbiol. 76,1028-1033. 

The second stage is the formation of dichloramines the monochloramines react further with chlorine. Dichloramine irritates the eyes and nose. 

Ammonia (NH3) and hypochlorite ion (OC1-) combine to produce three different chloramine species—that is, compounds that are derivatives of ammonia in which one or more of the hydrogen atoms has been replaced by a chlorine atom. In order of increasing degree of chlorine substitution, these chloramines are named monochloramine (NH2CI), dichloramine (NHCh), and nitrogen trichloride (NCI3) ... 

HOC6H4CH2CH(NH2)COOH + HOC1 HOC6H4CH2CH(NHCl)COOH (26) L-Tyrosine Monochloramine... 

An aromatic sulphonic acid amide-------NaCI° ----> A Monochloramine... 

Chamberlain E, Adams C (2006) Oxidation of sulfonamides, macrolides, and carbadox with free chlorine and monochloramine. Water Res 40 2517-2526... 

Chlorination and chloramination of a widely used antibacterial additive, triclo-san, which is used in many household personal care products, results in the formation of chloroform, 5,6-dichloro-2-(2,4-dichlorophenoxy)phenol, 4,5-dichloro-2-(2,4-dichlorophenoxy)phenol, 4,5,6-trichloro-2-(2,4-dichlorophenoxy)phenol, 2, 4-dichlorophenol, and 2,4,6-trichlorophenol [119]. The reaction of triclosan with monochloramine is slow, however, compared to chlorine [120]. The chlorophenox-yphenols are formed via bimolecular electrophilic substitution of triclosan. 

Choi J, Valentine RE (2002) Formation of N-nitrosodimethylamine (NDMA) from reaction of monochloramine a new disinfection by-product. Water Res 36(4) 817-824... 

Na C, Olson TM (2004) Stability of cyanogen chloride in the presence of free chlorine and monochloramine. Environ Sci Technol 38(22) 6037-6043... 

Reacts with chlorine forming chloramines monochloramine, dichloramine and nitrogen trichloride ... 

Chlorine forms carbonyl chloride, COCl with carbon monoxide suhuryl chloride SO2CI with sulfur dioxide and chloramines (monochloramine, NH2CI, and dichloramine, NHCI2) with ammonia. Chloramines are often found at trace concentrations in sewage wastewater following chlorine treatment. 

---