Nitrobenzene

Nitrobenzene, also known as nitrobenzol or oil of mirbane, is a poisonous organic compound with an almond odor and chemical formula C₆H₅NO₂. This oily water-insoluble liquid is mainly produced as a precursor to aniline but in the laboratory It is used as a solvent and as a mild oxidizing agent.

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Uses

Approximately 98% of nitrobenzene is consumed in the production of aniline.^[1] More specialized applications include rubber chemicals, pesticides, dyes, and pharmaceuticals. Nitrobenzene is also used in shoe and floor polishes, leather dressings, paint solvents, and other materials to mask unpleasant odors. Substitution reactions with nitrobenzene are used to form m-derivatives (Mannsville 1991; Sittig 1991)^{[citation needed]}. Redistilled, as oil of mirbane, nitrobenzene has been used as an inexpensive perfume for soaps. A significant merchant market for nitrobenzene is its use in the production of the analgesic paracetamol (also known as acetaminophen) (Mannsville 1991)^{[citation needed]}. Nitrobenzene is also used in Kerr cells, as it has an unusually large Kerr constant.

Nitrobenzene is readily converted to related derivatives such as azobenzene,^[2] nitrosobenzene.^[3], phenylhydroxylamine.^[4]

Production

Nitrobenzene is prepared by nitration of benzene. The classic method involves treatment of benzene with a mixture of concentrated sulfuric acid, water, and nitric acid, called "mixed acid." Its production is one of the most dangerous processes conducted in the chemical industry due to the exothermicity of the reaction (ΔH = −117 kJ/mol).^[1]

There were four producers of nitrobenzene in the United States in 1991: First Chemicals Corporation, Mobay, DuPont Chemicals, and Rubicon Inc. World capacity for nitrobenzene in 1985 was ca. 1.7×10⁶ tonnes.^[1]

Mechanism

The reaction pathway entails formation of an adduct between the Lewis acidic nitronium ion, NO₂⁺, and the arene. The nitronium ion is generated in situ via the reaction of nitric acid and an acidic dehydration agent, typically sulfuric acid:

HNO₃ + H⁺ ⇌ NO₂⁺ + H₂O

References

1. ^ ^{a b c} Gerald Booth "Nitro Compounds, Aromatic" in "Ullmann's Encyclopedia of Industrial Chemistry" 2007; John Wiley & Sons: New York.
2. ^ Bigelow, H. E.; Robinson, D. B. (1955). "Azobenzene". Org. Synth.; Coll. Vol. 3: 103. 
3. ^ G. H. Coleman, C. M. McCloskey, F. A. Stuart. "Nitrosobenzene". Org. Synth.; Coll. Vol. 3: 668. 
4. ^ O. Kamm. "Β-Phenylhydroxylamine". Org. Synth.; Coll. Vol. 1: 445.