Hydrocarbons, Aromatics

Aromatic hydrocarbons are all combustible. The lightest members of this class, benzene and substituted benzenes, have high enough vapor pressures and low enough flash points to be vapor explosion hazards.

Vigorous reactions, sometimes amounting to explosions, can result from the contact between these materials and strong oxidizing agents. They can react exothermically with bases and with diazo compounds. Substitution at the benzene nucleus occurs by halogenation (acid catalyst), nitration, sulfonation, and the Friedel-Crafts reaction.

Many aromatic hydrocarbons are poisons by inhalation and irritants to the skin and eyes. Some are poisons by skin contact. Aromatic hydrocarbons are very often carcinogenic (benzene is an example).

Compounds in this group contain the benzene nucleus. In benzene six carbon atoms form a ring maintained by alternating single and double bonds; each carbon atom is also bonded to a hydrogen atom. Aromatic hydrocarbons possess a single benzene nucleus with side-groups replacing one or more of the hydrogen atoms or in fused sets of two or more rings. They are common air contaminants.

Benzene, toluene, naphthalene, pyrene, anthracene, chrysene, acenaphthylene, xylene, benzo[a]pyrene, biphenyl, cumene, fluorene, phenanthrene.