Nitrobenzene

Overview
Nitrobenzene, also known as nitrobenzol or oil of mirbane, is a poisonous organic compound with an almond odor and chemical formula C6H5NO2. It may be found as either bright yellow crystals or an oily water-insoluble liquid.

It is used as a solvent and as a mild oxidizing agent. It is most frequently used specifically in the manufacture of aniline, but also used in the manufacture of insulating compounds and polishes.

Uses
While nitrobenzene is primarily used in the production of aniline and aniline derivatives, such as methylene diphenyl diisocyanate (MDI), it also finds use in the manufacture of 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). 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). Nitrobenzene is also used in Kerr cells, as it has an unusually large Kerr constant.

Production
There were four producers of nitrobenzene in the United States in 1991: First Chemicals Corporation, Mobay, DuPont Chemicals, and Rubicon Inc. In 1991, the estimated total production capacity of nitrobenzene in the U.S. was 617000 tonnes (Mannsville 1991).

The classic method for forming nitrobenzene is to react benzene with a mixture of concentrated sulfuric acid and nitric acid. This mixture of acids forms an electrophile which reacts with the benzene in an electrophilic aromatic substitution reaction. This reaction is often known as a nitration reaction.

The nitric acid is protonated by the sulphuric acid to form H2NO3+ which then loses water to form NO2+. The concentrated sulphuric acid has a high affinity for the water, this helps the reaction go.