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The U.S. National Institute for Occupational Safety and Health considers 4-nitrochlorobenzene as a potential occupational carcinogen. [7] The Occupational Safety and Health Administration set a permissible exposure limit of 1 mg/m 3 The American Conference of Governmental Industrial Hygienists recommends an airborne exposure limit of 0.64 mg/m 3 over a time-weighted average of eight hours.
Nitrochlorobenzene is typically synthesized by nitration of chlorobenzene in the presence of sulfuric acid: . C 6 H 5 Cl + HNO 3 → O 2 NC 6 H 4 Cl + H 2 O. This reaction affords a mixture of isomers.
Unlike the other isomers of nitrochlorobenzene, the meta isomer is not activated to nucleophilic substitution at the chlorine center. [1] However, 3-nitrochlorobenzene has other interesting reactivity. 3-Nitrochlorobenzene can be reduced to 3-chloroaniline with Fe/HCl mixture, the Bechamp reduction.
By virtue of the two nitro substituents, the chloride in DNCB is particularly susceptible to nucleophilic substitution, at least relative to simple chlorobenzene. In this way, the compound is a precursor to many other compounds. [4] [5] [6] In one example, DNCB is as a substrate in Glutathione S-Transferase, relevant to activity assays. [7]
1,3-Dinitrobenzene is accessible by nitration of nitrobenzene.The reaction proceeds under acid catalysis using sulfuric acid. The directing effect of the nitro group of nitrobenzene leads to 93% of the product resulting from nitration at the meta-position.
Chlorobenzene (abbreviated PhCl) is an aryl chloride and the simplest of the chlorobenzenes, consisting of a benzene ring substituted with one chlorine atom. Its chemical formula is C 6 H 5 Cl. This colorless, flammable liquid is a common solvent and a widely used intermediate in the manufacture of other chemicals.
The three possible arrangements of the nitro groups afford three isomers, 1,2-dinitrobenzene, 1,3-dinitrobenzene, and 1,4-dinitrobenzene. Each isomer has the chemical formula C 6 H 4 N 2 O 4 and a molar mass of about 168.11 g/mol. 1,3-Dinitrobenzene is the most common isomer and it is used in the manufacture of explosives .
Commonly, 2-nitrochlorobenzene is treated with ammonia to generate 2-nitroaniline, whose nitro group is then reduced: [4] ClC 6 H 4 NO 2 + 2 NH 3 → H 2 NC 6 H 4 NO 2 + NH 4 Cl H 2 NC 6 H 4 NO 2 + 3 H 2 → H 2 NC 6 H 4 NH 2 + 2 H 2 O