Benzene is volatile and highly flammable; it boils at 80.1°C, and melts at 5.5°C.
Benzene is present in small proportion in some crude oils and is made commercially from petroleum by the catalytic reforming of naphthenes in petroleum naphtha. It is also made from coal in the manufacture of coke. Benzene is used as a solvent in the manufacture of detergents, synthetic fibers, petrochemicals, and as a component of high-octane gasoline. It is also used as the starting material for a great variety of aromatic compounds, including phenol, styrene, aniline, and maleic anhydride. It is toxic by ingestion and inhalation, and may cause bone marrow problems or leukemia with prolonged exposure.
HistoryBenzene was first isolated by Michael Faraday in 1825, from the whale oil used in gaslights; he also determined that it had an empirical formula of CH. Eilhardt Mitscherlich synthesized benzene in 1834, and showed it to have a molecular formula of C6H6.
Many other compounds with similar properties to benzene were discovered in the 1800s, all having a low ratio of hydrogen to carbon. This usually indicates the presence of carbon-carbon double bonds, but these compounds did not undergo the reactions typical of alkenes under ordinary lab conditions. Since many of these molecules had pleasant aromas, they were called "aromatic compounds." The structure of benzene and its derivatives was a puzzle for many years, until Friedrich August Kekulé proposed the cyclic structure in the top diagram in 1866 (supposedly after having a dream about a snake biting its own tail). The term "aromatic" in organic chemistry now means that the molecule contains benzene, or its structural relatives.
Related category• ORGANIC CHEMISTRY
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