PICENE

Description

Picene, a polycyclic aromatic hydrocarbon (PAH) of environmental relevance has recently been predicted to be carcinogenic, based on quantum mechanical calculation, although in several animal studies no carcinogenicity could be detected.
Picene, a hydrocarbon found in the pitchy residue obtained in the distillation of peat-tar and of petroleum. This is distilled to dryness and the distillate repeatedly recrystallized from cymene It may be synthetically prepared by the action of anhydrous aluminium chloride on a mixture of naphthalene and ethylene dibromide, or by distilling α-dinaphthostilbene. It crystallizes in large colourless plates wi hich possess a blue fluorescence It is soluble in concentrated sulphuric acid with a green colour. Chromic acid in glacial acetic acid solution oxidizes it to picene-quinone, picene-quinone carboxylic acid, and finally to phthalic acid. When heated with hy driodic acid and phosphorus it forms hydrides of composition C22H34 and C22H36.

Definition

ChEBI: An ortho-fused polycyclic arene consisting of five fused benzene rings. It is obtained during the distillation of petroleum.

Carcinogenicity

Dermal application of picene in an early design limited study on mice gave negative results for carcinogenicity. More recently, picene gave positive results when tested in three dermal application studies on mice, two of which were initiation–promotion experiments. Subcutaneous injection into newborn and adult mice and young rats gave positive results in mice but negative results in rats.