Benzidine dyestuff intermediates

Use Organic synthesis dyestuffs (intermediate in the manufacture of the dry colors generally referred to as Hansa and benzidine yellows). 

Case, R. A., Hosker, M. E., Me, D. D., and Pearson, J. T. (1954). Tumours of the urinary bladder in workmen engaged in the manufacture and use of certain dyestuff intermediates in the British chemical industry. I. The role of aniline, benzidine, alpha-naphthylamine, and beta-naphthylamine. Br J Ind Med 11, 75-104. 

Nitrobenzene is used mainly as an intermediate in the production of aniline. It also forms the basis for the production of 3-chloronitrobenzene, m-nitrobenzene-sulfonic acid and p-aminophenol its earlier importance in the production of the dyestuff intermediate benzidine is insignificant today, due to the carcinogenicity of the latter. The industrial production of nitrobenzene is achieved by isothermal nitration of benzene. Mixed nitration acid, composed of 40% HNO3, 40% H2SO4 and 20% water, is used as the nitrating medium. Whereas the process was originally carried out batchwise, continuous operation predominates today in plants with a capacity up to 100,000 tpa. Stainless steel equipment is used, which is resistant to corrosion due to a passivation effect. 

The past experience of the dyestuff industry in its use of dye intermediates such as ( -naphthyl amine and benzidine (4), known human bladder carcinogens (334—343), have led to studies as to whether or not handlers of dyes are exposed to medical ha2ards such as cancer, dermatitis, and other disorders (344-360). 

The largest user of phenol in the form of thermosetting resins is the plastics industry. Phenol is also used as a solvent and in the manufacture of intermediates for pesticides, pharmaceuticals, and dyestuffs. Styrene is used in the manufacture of synthetic rubber and polystyrene resins. Phthalic anhydride is used in the manufacture of DMT, alkyd resins, and plasticizers such as phthalates. Maleic anhydride is used in the manufacture of polyesters and, to some extent, for alkyd resins. Minor uses include the manufacture of malathion and soil conditioners. Nitrobenzene is used in the manufacture of aniline, benzidine, and dyestuffs and as a solvent in polishes. Aniline is used in the manufacture of dyes, including azo dyes, and rubber chemicals such as vulcanization accelerators and antioxidants. 

Yield.—65% theoretical (48 gms.). Plates M.P. 128° slightly soluble in water soluble in alcohol and in benzene salts about 5 times more soluble than those of benzidine intermediate for dyestuffs. (B., 17, 467 20, 2017.)... 

Benzidine derivatives like 3,3 -dimethylbenzidine and 3,3 -dimethoxybenzidine (o-dianisidine) (Figure 27), are used as dyes or intermediates for dyestuffs or pigments (e.g.. Trypan Blue, Acid Red 14, and Direct... 

Azo dyes based on the aromatic intermediate benzidine were invented in 1884. These were the first synthetic dyes that adhered to cotton fabrics without the need for a fixing agent (mordant). For this reason they were known as direct or substantive dyes. The first member was discovered by Paul Bottiger, at Bayer. From benzidine (25) and naphthionic acid (20) he obtained a red bisazo dyestuff (26)41 see Scheme 9. 

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