Cyclopentene is a chemical compound with the formula (CH2)3(CH)2. It is a colorless liquid with a petrol-like odor. It has few applications, and thus is mainly used as a minor component of gasoline, present in concentrations of less than 1%. It is one of the principal cycloalkenes.

History and synthesis

Cyclopentene was first prepared by Carl Gärtner in 1893 from iodocyclopentane with potassium hydroxide. He named it pentamethenylene. Cyclopentene is produced industrially in large amounts by steam cracking of naphtha. In the laboratory, it is prepared by dehydration of cyclopentanol. Substituted cyclopentenes are the product of the vinylcyclopropane-cyclopentene rearrangement. It can also be produced by the catalytic hydrogenation of cyclopentadiene.

Reactions

The polymerization of cyclopentene by Ziegler-Natta catalysts yields 1,3-linkages, not the more typical 1,2-linked polymer. Palladium-catalyzed hydrocarboxylation of cyclopentene gives cyclopentanecarboxylic acid: