Oxidants dichloramine

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. 

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). 

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. 

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). 

The parent compound, cyclic diazomethane , was first obtained from formaldehyde, ammonia and chloramine by dichromate oxidation of the initially formed higher molecular diaziridine-formaldehyde condensation product (61TL612). Further syntheses of (44) started from Schiff bases of formaldehyde, which were treated with either difluoramine or dichloramine to give (44) in a one-pot procedure. Dealkylation of nitrogen in the transient diaziridine was involved (65JOC2108). 

Dichloramine, 23 101, 102-103 Dichloramine-B, 23 109 2V,2V-Dichloramines, 23 106 Dichloramine-T, 23 109 Dichlorine dioxide, oxidation state and stability, 8 545t Dichlorine heptoxide, 18 275... 

Consider the formation of the nitrate ion. The oxidation state of nitrogen in the nitrate ion is +5. Thus, this ion would not be formed from ammonia, because this would need the abstraction of eight electrons. If it is formed from the monochloramine, it would need the abstraction of six electrons, and if formed from the dichloramine, it would need the abstraction of four electrons. Thus, in the chloramine reactions with HOCl, the nitrate is formed from the dichloramine. We will, however, compare which formation forms first from the dichloramine trichloramine or the nitrate ion. The oxidation state of the nitrogen atom in trichloramine is -i-3. Thus, to form the trichloramine, two electrons need to be abstracted from the nitrogen atom. This may be compared to the abstraction of four electrons from the nitrogen atom to form the nitrate ion. Therefore, the trichloramine forms first before the nitrate ion does. 

Solution When dichloramine oxidizes a substance, its chlorine atom is reduced to chloride And, as gleaned from its formula, the nitrogen must be converted to the NH4 ion. Thus, the oxidation-reduction reaction using only half the reaction is... 

Dichloramine is an unstable compound and decomposes by several mechanisms. Most important is an oxidation mechanism producing Cl and N2 resulting in a loss of N2. Under neutral and basic conditions, decomposition of NHCI2 is thought to proceed by the coupled reactions (Brezonik, 1994) (B is... 

Figure 11.13. General scheme of breakpoint chlorination difference between total residual Cl and chlorine dose reflects chlorine demand, primarily from ammonium and amines. Before breakpoint, most Cl is in combined forms, primarily mono- and dichloramine after the breakpoint, the combined residual consists of slow-reacting organic chloramines. Added Cl remains in free form after the breakpoint. Sharpness of breakpoint and minimum observed Cl concentration depend on pH, temperature, and time of reaction. Loss of residual Cl at breakpoint is caused by oxidation of di- and trichloramines to Nj according to reactions 33a and 33b and other reactions. (Adapted from Brezonik, 1994.)...

The presence of other oxidizing agents such as manganese(IV) can interfere with the chlorine determination if the titration is performed at pH<3.5. Under this condition, the organic chloramines are often converted to either monochloramine or dichloramine, resulting in positive errors for these substances. Also, the volatilization of chlorine compounds can result in low recoveries. This can occur due to the violent agitation or aeration of some of the chloramines prior to the addition of iodide. 

Figure 11.16 Revised mechanism for formation of NDMA from dimethylamine during water chlorination by chloramine or by other chlorinating agents with ammonia present. The first step in disproportionation of chloramines to dichloramine (Equation [11.3]). (a) The dichloramine then reacts with dimethylamine in a fashion analogous to the reaction of chloramine in the original mechanism (Figure 11.15) to form chloro-NDMA. (b) Subsequent oxidation of the substituted hydrazine by oxygen competes strongly with oxidation by chloramine. Reproduced from Schreiber, Env. Set Technol 40, 6007 (2006), copyright (2006) with permission of the American Chemical Society.

The rate of oxidation of some a-amino acids to the corresponding aldehydes, ammonia, and carbon dioxide by A-chloronicotinamide (NCN) in acidic medium is first-order in both oxidant and HCl and fractional order in amino acid nicotinamide, the reduction product of NCN, has a retarding effect on the rate. Molecular chlorine has been postulated as the reactive oxidizing species in the reaction. " Deuterium solvent isotope effects suggest decomposition through two processes in the oxidation of Ala-Gly and Pro-Gly by aqueous chlorine elimination then imine hydrolysis in alkaline medium and in acidic medium the chloramine dipeptide disproportionates to N, A-dichloramine dipeptide. 

Chloramine, like chlorine, is an oxidizing biocide used for disinfection. Three species collectively make up chloramines, also known as combined chlorine monochloramine, NH Cl dichloramine, NHCl and nitrogen trichloride (trichloramine), NCI3. Of these, monochloramine has the highest standard reduction potential furthermore, it is less prone to impart chlorinous taste and odor to water like other forms of chloramine. As a result, monochloramine is preferred for disinfection applications. 

Organic compounds generating hypochlorous acid often possess a mono or gem dichloro amine or amide group. They are more oxidizing than hypochlorite. For example, dichloramine T (N-dichloroparatoluenesulfonamide) ... 

Chlorosulfonic acid is employed in the manufacture of synthetic detergents such as sulfates of alkenes or unsaturated oils, polyoxypropylene glycol, long chain alcohols, alkylarenes or alkyl diphenyl ethers. It is also extensively used in the manufacture of sulfonamide antibacterials (sulfa dmgs), diuretics and other pharmaceuticals, pesticides, artificial sweeteners (saccharin), disinfectants (chloramine and dichloramine T), plasticizers, dyes and pigments, sulfonyl polymers as plastics, and ion exchange resins. Chlorosulfonic acid is an oxidizing and... 

Reaction of Pb(C2H5)4 with chloramine-T and dichloramine-T is used for decontamination purposes [57]. Pb(C2H5)4 is removed from waste waters by oxidation with CIO2 in the presence of a catalyst [150]. 

The N,N-dichlorosulfonamide copolymer used here is a high molecular equivalent of the known low molecular equivalent of oxidants, such as the aromatic Dichloramine T. In literature we found the information, that monochloramine T is used by a redoxymetric method... 

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