Chloramine irradiation

Note Chloramines do not require exposure to chlorine gas before application of o-toluidine. A range of halogen-containing substances (e.g. bromazine, hexachloro-cyclohexane isomers) can be detected with o-toluidine (1 % in ethanol) after subsequent irradiation with UV light (k = 254 or 366 nm 10-15 min) [1, 8]. 

Ultraviolet (UV) irradiation is used to destroy bacteria and reduce organic compounds (measured as TOC) as well as destruction of chlorine and chloramines. This technique involves passing water over a UV lamp that is operating at a specific wavelength of energy. 

An early version was the Hofmann-Loffler-Freytag reaction (Scheme 1). Irradiation of a chloramine in acid leads to formation of the aminium radical, which can abstract a hydrogen to generate a caibon radical. Then the resulting carbon radical abstracts chlorine from another protonated chloramine, producing a chlorinated carbon and regenerating the chain-carrying radical. On treatment with base, the product... 

Irradiation of the nitrosoamine (542) or the chloramine (543) in acidic solution proceeds with a concerted Grob fragmentation , giving the corresponding pregnan-20-one (544). ... 

The one-pot three-component reaction of polyethylene glycol-supported acrylate 623 with aldehydes 621 and hydrazines 622 in the presence of chloramine-T followed by methanolysis afforded pyrazolines 624 in good yields and high purities (Scheme 77) <2003SL1467>. 1,3-Dipolar cycloaddition of resin-supported acrylic acid 625 with the nitrilimines generated in situ by oxidation of the aldehyde phenylhydrazones with (diacetoxy)iodobenzene under microwave irradiation gave 626, which was converted into l-phenyl-3-substituted-2-pyrazolinyl-5-carboxylates 627 (Scheme 78) <2004SC3521>. 

As in the case of 5a-conanine, the Loeffler-Freytag reaction was applied in the synthesis of dihydroconessine by Corey and Hertler (138, 139). Starting from 3)3-acetoxy-20a-aminopregn-5-ene (48) they obtained 3j8-dimethylamino-20a-methylamino-5a-pregnane (L) by obvious reactions. The base was converted to chloramine CLXVI which upon irradiation with UV-light afforded the 18-chloro derivative CLXVII cyclizing readily to dihydroconessine (CXXVI). 

One of the important issues in water and wastewater disinfection is the formation of disinfection by-products, their environmental consequences, and prevention, control, and minimization of them. The major disinfectants are chlorine, chlorine dioxide, ozone, chloramines, and UV irradiation. It is well recognized that disinfection by chlorine, the most commonly used disinfectant, can cause formation of many DBFs, even though it is effective and the cost is low. 

A variety of substrates were examined by Chanda [85] for aziridination with chloramine-T 150 and Bromamine-T 148 in the presence of a copper catalyst. It is interesting to note that aziridination did not occur with the less reactive cinna-mates 147 in the presence of CuCh and CuBr2 (Scheme 5.41). The reaction did, however, proceed under the action of microwave irradiation with CuBr2 to yield the aziridine 149, albeit in poor yield. 

The photochemical reactivity of [Rh NH3)5(N3)] " has proven especially interesting, for HCl solutions of the azidopentaammine ion undergo a ligand-centered reaction, releasing Nj gas, and generating the chloramine complex (equation 139). Minor products include [Rh(NH3)j] , [Rh(NH3)j(NH20H)] + and [Rh H3)5(H20)] +, and the ratio of products depends on the solution conditions and wavelength of irradiation. A coordinated nitrene mechanism, similar to that proposed for the thermal decomposition of Ru and azides was proposed, and is... 

The Ph2PS radical is produced by Jlf-irradiation of diphenylthiophos-phine, and under y-irradiation trichlorosilane brings about the desulphura-tion of phosphine sulphides to phosphines and of phosphorothionates to phosphites. Chloramine-T has been found to be a useful oxidant for distinguishing between a variety of structural units, particularly in phosphorus-sulphur compounds. ... 

Irradiation acetic acid o-a-Chloro-N-heterocyclics from ethylene-N-chloramines... 

Over the years, public water systems have used various alternatives to chlorine disinfection. The more common alternatives include (1) chloramines, (2) Ozone, (3) Chlorine Dioxide, and (4) Ultraviolet irradiation. 

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