Chloramine formation

Acetic anhydride-nitric acid mixtures are extensively used for chloride-catalyzed nitrations. Other nitrating agents have been used and involve similar sources of electropositive chlorine for intermediate chloramine formation. 4,10-Dinitro-4,10-diaza-2,6,8,12-tetraoxaisowurtzitane (TEX) (40), an insensitive high performance explosive (VOD 8665 m/s, d = 1.99 g/cm ), is synthesized by treating the dihydrochloride salt of the corresponding amine (39) with strong mixed acid. ... 

Chloramines were analysed in additional experiments by selective spectrophotomet-rical procedure (HACH method 10171). When the chloride concentration is nearly zero, de facto no chlorine or chloramines (measured as the difference between total and active chlorine) are visible. Ammonium is formed linearly in the cathodic reaction (A). In the second case B, active chlorine is consumed by the ammonium with chloramine formation. After switching off the electrolytic current, this reaction continues until all the chlorine is reacted. 

Despite that the MPO-catalyzed oxidation of halides seems to employ the same mechanisms active in primary production of the respective hypohalous acids, the final products of peptide and protein oxidation vary, depending on the halide ion employed iodides and bromides when used as substrates yield stable bromo-and iodotyrosine derivatives, whereas direct chlorination of the available free amino moieties and semistable chloramines formation predominate when Cl is oxidized as the substrate (S54, Z3). The chlorination is a unique function of polymorphonuclear neutrophilic leukocytes (W6, Z2). 

The other amino acid reacting with HOC1 is tyrosine. At pH ranging from 3.5 to 6.0, HOC1 reacts with A-acetyltyrosine to produce S -chloro derivative (Fig. 8). If the HOCl/N-acetyltyrosine molar ratio exceeds 10, 3/5/-dichlorotyrosine formation is observed. The chlorotyrosine formation is slow compared to chloramine formation or tryptophan oxidation reaction rate. The optimal conditions for tyrosine... 

Changes in the number of free amino residues alter the modified proteins susceptibility to proteolysis. Albumin chlorination and /V-chloramine formation decreases susceptibility to trypsin digestion. Removing of chloramine residues by treatment with thiosulfate shows that chlorination alters albumin properties by a biphasic mode the reversible chlorination and removal of chloramine moieties markedly increases albumin susceptibility to proteolysis, whereas chlorination produces the irreversible loss of amino moieties and carbonyl group formation effects decrease in albumin susceptibility to trypsin digestion. The effect is related to the number of lost amino residues. A similar relationship was observed for IgG. Fibrinogen and protamine, on the other hand, did not show dependence between chlorination and proneness to trypsin proteolysis (06). 

Trypsin attacks the peptide bonds following the basic amino acids arginine and lysine. Formation of chloramines decrease trypsin binding sites, which causes a decrease in protein susceptibility to trypsin digestion. On the other hand, chloramine formation from free amino residues may induce changes in tertiary albumin structure, revealing some normally inaccessible amino residues. Therefore, removal... 

Reactions with ammonia and optimum pH range for chloramine formation. 

In waters and wastewaters, organic amines and their decomposition products such as ammonia may be present, hi addition, ammonia may be purposely added for chloramine formation to produce chlorine residuals in distribution systems. Also, other organic snbstances snch as organic amides may be present as well. Thus, from point A to B, chloro-organic compounds and organic chloramines are formed. Ammonia will be converted to monochloramine at this range of chlorine dosage. 

Chloramine formation and oxidation of ammonia by chlorine combine to create a unique dose-residual curve for the addition of chlorine to ammonia-containing solutions (Fig. 7-24). As the chlorine dose increases, the chlorine residual at first rises to a maximum at a [CI2] dose to [NH3] molar ratio of about 1.0. As the chlorine dose is increased further, the chlorine residual falls to a value close to zero. The chlorine dose corresponding to this minimum is called the "breakpoint" dose, and it occurs at a molar ratio of 1.5 1 to 2 1, depending upon solution conditions. The primary reaction that causes the residual chlorine concentration to decrease and thus to form the breakpoint is the breakpoint reaction, which can be represented as... 

The principal reactions for chloramine formation are presented below ... 

In Reaction 1, the formation of sodium hypochlorite is spontaneous with in situ mixing of chlorine and aqueous caustic solution. In Reaction 2, the reaction rate for chloramine formation is rapid relative to the formation of hydrazine in Reaction 3. Because the decomposition rates are relatively insensitive to temperature. Reaction 3 is operated at 130°C to speed up the rate-determining step. Excess ammonia is used to minimize the hydrazine-chloramine decomposition. 

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