Benzene

 

 

Benzene A colorless, liquid, inflammable, aromatic hydrocarbon of chemical for­mula C6H6 which boils at 80.l°C (176.2°F) and freezes at 5.4-5.5°C (41.7-41.9°F). In the older American and British technical literature benzene is designated by the Ger­man name benzol. In current usage the term benzol is commonly reserved for the less pure grades of benzene.

Benzene is used as a solvent and particularly in Europe as a constituent of motor fuel. In the United States the largest uses of benzene are for the manufacture of styrene and phenol. Other important outlets are in the production of dodecylbenzene, aniline, maleic anhydride, chlorinated benzenes (used in making DDT and as moth flakes), and benzene hexachloride, an insecticide.

The six carbon atoms of benzene, each with a hydrogen atom attached, are arranged symmetrically in a plane, forming a regular hexagon. The hexagon symbol, commonly used to represent the structural formula for benzene, implies the presence of a carbon atom at each of the six angles and, unless substituents are attached, a hydrogen at each carbon atom. Whereas the three double bonds usually included in the formula are convenient in accounting for the addition reactions of benzene, present evidence is that all the carbon-to-carbon bonds are identical.

Nearly all commercial benzene is a product of petroleum technology. The gasoline fractions obtained by reforming or steam cracking of feedstocks from petroleum contain benzene and toluene which can be separated economically. Benzene may also be produced by the dealkylation of toluene.

Benzene is a toxic substance, and prolonged exposure to concentrations in excess of 35–100 parts per million in air may lead to symptoms ranging from nausea and excess fatigue to anemia and leukopenia.

 

 

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