Transformations benzidine

Benzidine chemistry involves reduction. The nitro precursor is reduced either by zinc and alkali or electrolyticaUy to the hydrazo intermediate, which is then transformed to the benzidine by treatment with acid. 

Direct Black 38 Mixed microbial culture isolated from an aerobic bioreactor treating textile wastewater The dye was transformed into benzidine and 4-aminobiphenyl followed by complete biodegradation of these toxic intermediates [134]... 

The limited information that is available suggests that 3,3 -dichlorobenzidine may photolyze in water to yield benzidine, which is more photostable yet still toxic. It does not appear that the chemical is susceptible to any other transformations in water except protonation by acid-base reactions. 

The removal of potassium cations makes the results of the liquid-phase and electrode reactions similar. In the presence of crown ether, the eight-membered complex depicted in Scheme 2.16 is destroyed. The unprotected anion-radicals of azoxybenzene are further reduced by cyclooctatet-raene dianion, losing oxygen and transforming into azodianion. The same particle is formed in the electrode reaction shown in Scheme 2.13. In the chemical reduction, stabilization of azodianion is reached by protonation. Namely, addition of sulfuric acid to the reaction results in the formation of hydrazobenzene, which instantly rearranges into benzidine (4,4 -diamino-l,l"-diphenyl). The latter was isolated from the reaction, which proceeded in the presence of crown ether. 

Nucleophiles, when they are used in the presence of cupric perchlorate, capture the cation-radicals initially formed. Instead of benzidines, the para-substituted dialkylanilines were obtained. In this a manner, A,A-dialkylanilines with halo or thiocyanato moieties in para positions were prepared in good yields under the same (simple) conditions. Scheme 7.13 illustrates the sequence of the transformations observed. The products are useful intermediates in the synthesis of dyes, drugs, and color cinema formulations. 

This work was extended by Elbs and his pupils,1 and the processes were protected by patents.2 Subsequently alcohol was dispensed with and aqueous caustic soda employed. For example, an emulsion of nitrobenzene in 10 per cent, aqueous sodium hydroxide may be reduced with a cathode of lead or nickel in a porous earthenware cell, with a current density of 10-12 amps, per dm.2 An anode of graphite or lead may be employed in an outer containing vessel filled with sodium hydroxide solution or sodium sulphate. Azo- or hydrazobenzene is obtained according to the quantity of electricity passed through, and the azobenzene emulsion can be transformed into benzidine by acidifying the cathode liquor and completing the reduction.4... 

Although several peroxidase enzymes obtained from plant, animal, and microbial sources have been investigated for their ability to catalyze the removal of aromatic compounds from wastewaters, the majority of studies have focused on using HRP. In particular, it has been shown HRP can transform phenol, chlorophenols, methoxyphenols, methylphenols, amino-phenols, resorcinols, and various binuclear phenols [7], HRP was also used for the treatment of contaminants including anilines, hydroxyquinoline, and arylamine carcinogens such as benzidines and naphthylamines [7,8]. In addition, it has been shown that HRP has the ability to induce the formation of mixed polymers resulting in the removal of some compounds that are either poorly acted upon or not directly acted upon by peroxidase [7], This phenomenon, termed coprecipitation or copolymerization, has important practical implications for wastewaters that usually contain many different pollutants. This principle was demonstrated when it was observed that polychlorinated biphenyls (PCBs) could be removed from solution through coprecipitation with phenols [20]. However, this particular application of HRP does not appear to have been pursued in any subsequent research. 

Quinamines having no substituents at the para-position of the aniline ring gave 4-aminodiphenyl ethers 77 as the principal products in almost quantitative yields. The behavior of quinamines 76 and their geometric features as well as the kinetic characteristics of the reaction make this transformation very similar to the well-known benzidine rearrangement (Section III.B.l). Like the latter, the mechanism of the quinamine rearrangement involves a transition state that resembles a sandwich of two rings (jr-complex)129. 

If, in hydrazo-compounds, the para position to the imido (NH) group is occupied as, e.g., in p-hydrazotoluene, then the benzidine transformation cannot occur. ... 

Some examples of a benzidine-type of rearrangement are known for N-arylamines which, to some extent, may be considered as analogues of hydrazo compounds. Thus, 1-anilinoimidazole (279), on heating in concentrated hydroxhloric acid, is transformed to 4(5)-p-aminophenyl derivative (280) (70ZC289). 

C-labelled Direct Blue 6 (17) and Acid Red 114 (18), bis-azo biphenyl dyes, possible human carcinogens2 3b, needed in order to study their distribution and biological transformations in animals, have been prepared24 from uniformly ring-labelled 14C-benzidine and 14C-3,3 -dimethylbenzidine according to equations 7 and 8. 17 has been prepared by reacting the diazotized benzidine with two equivalents of H acid under basic conditions to insure the occurrence of the attack of the electrophilic species at the ortho... 

The mechanism of carcinogenicity of benzidine is thought to involve its metabolic transformations forming reactive intermediates binding to DNA. Such DNA adducts have been identified in rodent liver. It tested positive in most genotoxic tests. Its carcinogenicity may possibly be related to the slow rate of liver detoxification by acetylation allowing activation of benzidine or its metabolites in urine (Whysner et al. 1996). 

Other cases are described in Section 13.5 under the heading Lethal examples . Thus fluoroacetic acid is transformed to fluorocitric acid which blocks the enzyme aconitase. Several amines, such as benzidine and 2-aminonaph-thalene are converted to carcinogenic hydroxylamines and polycyclic hydrocarbons such as benzopyrene are converted to carcinogenic epoxides. The liver converts carbon tetrachloride to a free radical which causes liver necrosis (Slater, 1966). 

In this method, a polymer is prepared which has certain struc-tiiral features which can be chemically transformed to dye structures in one or more steps. Perhaps the most common class of dyes that have been so synthesized on a polymer backbone is the azo dyes, which are simply formed by the coupling of a polymeric aryl diazon-ium salt with an activated aromatic system. The former are prepared from polymeric aromatic amines by diazotization. Thus polymers and copolymers of 2,2 -di vinyl benzidine (XVl) have been diazotized and coupled with sodium naphthionate, sodium anthranilate and sulfanilic acid to give polymeric azo dyes which act as pH indicators,... 

Bedekar and co-workers [4] characterised a series of polyaromatic diamines including polymers of o-chloroaniline, benzidine, 4,4 diaminodiphenyl ether and diaminodiphenyl methane using a variety of techniques including X-ray photoelectron spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and elemental analysis. They found that polymers of diamine compounds had an additional S and O in the form of sulfate ions in the polymer matrix. 

Polychlorinated Biphenyls. There are several sources of polychlorinated biphenyls (PCBs) in museums. Often these are first discovered by waste-disposal companies that pick up a museum s hazardous refuse. Disposal companies usually analyze solvent, paint, and other hydrocarbon wastes because disposal of PCB-contaminated material is vastly more complex and expensive than disposal of ordinary wastes. In some cases, museum waste has been contaminated by fluids leaking from transformers or fluorescent light ballasts, both of which are common sources of PCBs. However, on two occasions of which the present author is aware, the contamination was from Arochor slide-mounting medium (a material which contains PCBs and polychlorinated triphenyls) and/or PCB-contaminated pigments such as phthalocyanine blue and green, and diarylide (benzidine) yellow. 

A review of the reactions and cationoid skeletal transformations in the series of polyfluoroarenes has been reported. The monoprotonated mechanism of the benzidine acid-catalysed rearrangement of hydrazobenzene has been compared with the diproto-nated mechanism monoprotonation results in concerted closed-shell sigmatropic shift, whereas diprotonation leads to a stepwise radical cation recoupling. ... 

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