Nitration chloramines

Niiraiion by the "dehydration" of the am.ne nitrate Nitration of priir.arv amines by acylation The formation of nitramines through chloramines Nitration by niirolysis... 

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). 

Potassium peroxymonosulfate, introduced in the late 1980s, is finding increasing use as an auxiUary oxidant for shock treatment and oxidation of chloramines. Sodium peroxydisulfate is also being sold for shock treatment, however, it is less reactive than peroxymonosulfate. Mixtures of sodium peroxydisulfate and calcium hypochlorite can be used for shock treatment (28). Disadvantages of peroxymonosulfate and peroxydisulfate are they do not provide a disinfectant residual and peroxymonosulfate oxidizes urea and chloramines to nitrate ion, which is a nutrient for algae. 

The formation of chloramine as an intermediate, followed by reaction with nitric acid to produce the corresponding nitramine and HOC1, may explain the catalytic action of HC1 in the nitration of amines... 

Treatment of municipal water with chlorine and ammonia results in the formation of chloramines, a long-lasting disinfectant. Too much ammonia, however, enhances nitrification by bacteria in the water, which, in turn, increases the nitrate and nitrite levels. High nitrate and nitrite levels in drinking water is a health hazard, particularly for infants. 

Chemical/Physical. Under atmospheric conditions, the gas-phase reaction of o-xylene with OH radicals and nitrogen oxides resulted in the formation of o-tolualdehyde, o-methylbenzyl nitrate, nitro-o-xylenes, 2,3-and 3,4-dimethylphenol (Atkinson, 1990). Kanno et al. (1982) studied the aqueous reaction of o-xylene and other aromatic hydrocarbons (benzene, toluene, w and p-xylene, and naphthalene) with hypochlorous acid in the presence of ammonium ion. They reported that the aromatic ring was not chlorinated as expected but was cleaved by chloramine forming cyanogen chloride. The amount of cyanogen chloride formed increased at lower pHs (Kanno et al., 1982). In the gas phase, o-xylene reacted with nitrate radicals in purified air forming the following products 5-nitro-2-methyltoluene and 6-nitro-2-methyltoluene, o-methylbenzaldehyde, and an aryl nitrate (Chiodini et ah, 1993). 

If nitration under acidic conditions could only be used for the nitration of the weakest of amine bases its use for the synthesis of secondary nitramines would be severely limited. An important discovery by Wright and co-workers " found that the nitrations of the more basic amines are strongly catalyzed by chloride ion. This is explained by the fact that chloride ion, in the form of anhydrous zinc chloride, the hydrochloride salt of the amine, or dissolved gaseous hydrogen chloride, is a source of electropositive chlorine under the oxidizing conditions of nitration and this can react with the free amine to form an intermediate chloramine. The corresponding chloramines are readily nitrated with the loss of electropositive chlorine and the formation of the secondary nitramine in a catalytic cycle (Equations 5.2, 5.3 and 5.4). The mechanism of this reaction is proposed to involve chlorine acetate as the source of electropositive chlorine but other species may play a role. The success of the reaction appears to be due to the chloramines being weaker bases than the parent amines. 

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. ... 

This method was originally suggested by Berg [39]. It consists in acting with silver nitrate on chloramines ... 

The intermediate formation of chloramine explains the catalytic action of hydrochloric acid in the nitration of amines, as mentioned above. The following reaction mechanism was drawn up by Wright [41]... 

Thus hydrocliloric acid reacts in the presence of nitric acid to yield chlorine acetate (a)—a compound with cationic chlorine. The latter in turn forms a chloramine (b) which is nitrated to a nitramine (c). 

Lhe elemental halogens as well as NCS and NBS, N-ehloroben-zotriazole. chloramine-T. MCPBA, periodic acid, and such hea-vy-mctal oxidants as thallium(IIl) nitrate or CAN... 

As stated in the introduction, chloramine-T (where T denotes three crystalline water molecules) is a commonly used nitrene precursor, which is commercially available and costs less than do most other nitrene sources. The benefit of a silver salt in nitrene transfer reactions with chloramine-T is surprisingly simple. Because silver chloride is insoluble in most solvents, substoichiometric amounts of silver salts (like silver nitrate) can be used to remove the chloride from chloramine to facilitate the release of a free nitrene radical, which can aziridinate olefins. Since the amount of silver is near stoichiometric, it should not be called silver-based catalysis, although turnover numbers (TONs) higher than 1 have been observed in some cases. 

Nitrate ions are allowed in German drinking water up to the limiting concentration of 50 ppm. The limiting concentration for nitrite and ammonium are 0.1 ppm (water works) and 0.5 ppm, respectively. Chloramination is not permitted. Hundreds of publications exist in the field of nitrate electrolysis in acidic, neutral, and alkaline media, mostly for nitrate concentrations in the gL 1 range. Depending on the conditions, the formation of nitrite, ammonium, N-O, N-H components and... 

Using BDD anodes and MIO cathodes, enrichment of ammonia was also observed - in contradistinction to other studies using higher ammonium concentration and an Ir02 anode (Kim et al. 2005). In the combination of BDD anode/BDD cathode, nitrite was oxidised but only relatively slowly. When nitrate was electrolysed, its depletion was lower than 1 ppm for current densities lower than 200 A m-2. An explanation for the relatively low reaction rate between radicals and nitrite is the assumption that ozone or radicals are consumed in faster reactions such as peroxide formation and chlorine oxidation. OH radicals are also able to oxidise chloramines (Huie et al. 2005). 

In 2001, Rai and co-workers (114) reported a silver-mediated aziridination of olefins in THF with Chloramine-T. In their case, aprotic solvents gave better yields versus protic solvents. Then, in 2003, Komatsu and co-workers (115) used similar conditions and found no reaction in THF (solvent) while they detected 70% conversion in CH2CI2. Silver nitrate (AgNOs) was required stoichiometrically in this transformation. Komatsu proposed a nitrene-radical mechanism based on the fact that the reaction shut down in the presence of oxygen. They designed a model reaction using 1,6-dienes, and as they expected, bicyclic pyrrolidines were isolated as products instead of aziridines. The role of silver in this reaction is not clear and most likely a free nitrene radical is released with the precipitation of silver(I) chloride (Fig. 18). 

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. 

As the curve continues to go downhill from point B, the dichloramine converts to the trichloramine, the conversion being complete at the lowest point indicated by breakpoint. As shown, this lowest point is called the breakpoint. In addition, nitrates will also be formed from the dichloramine before reaching the breakpoint. In fact, other snbstances wonld have been formed as decomposition products from monochloramine and dichloramine, as well as other snbstances would have been formed as decomposition prodncts from the chloro-organic compounds and organic chloramines. 

This method w as used in a synthesis of m-jasmone to eifect removal of a dithiokelal group.Thus oxidation of (1) with ceric ammonium nitrate gave undecane-2,5-dione (2) in 80% yield. In this case use of chloramine-T (this volume) gave (2) in 67.3 % yield. 

ETHYLENETHIOKETALS Chloramine-T. E/C-GLYCOLS Ceric ammonium nitrate. METHYL ESTERS 1,5-Diazabicyclo-14.3.0] nonene-5. 1,5-Diazabicyclo[5.4.0]-undcccnc-5... 

OXIDATION, REAGENTS Dimethylsulf-oxide-Acetic anhydride. 1-Amyl hydroperoxide. N-Bromosuccinimide. Ceric ammonium nitrate. Chloramine. o-Chlo-ranil. 1-Chlorobenzotriazole. N-Chloro-succinimide-Dimethyl Sulfide. Chromic acid. Chromic anhydride. Chromyl chloride. Cobalt(ll) acetate. Cupric acetate monohydrate. Cupric nitrate-Pyridhic complex. 2,3-Dichloro-5,6-dicyano-l, 4-benzoquinonc. Dicyclohcxyl-18-crown-... 

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