| polycyclic hydrocarbons, aromatic | <chemical> A major group of unsaturated cyclic hydrocarbons containing two or more rings. The vast number of compounds of this important group, derived chiefly from petroleum and coal tar, are rather highly reactive and chemically versatile. The name is due to the strong and not unpleasant odour characteristic of most substances of this nature. Pharmacological action: carcinogens. (12 Dec 1998) |
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| hydrocarbons, aromatic | Organic compounds composed exclusively of carbon and hydrogen. They are unsaturated hexagonal ring structures with a closed conjugated system of double bonds that gives them the characteristic chemical properties of the parent aromatic hydrocarbon, benzene. (12 Dec 1998) |