Cyclopentane (also called C pentane)[4] is a highly flammable alicyclic hydrocarbon with chemical formula C5H10 and CAS number 287-92-3, consisting of a ring of five carbon atoms each bonded with two hydrogen atoms above and below the plane.

It is formed by cracking cyclohexane in the presence of alumina at a high temperature and pressure.

[6][7] While cyclopentane is not typically used as a refrigerant, it is common for domestic appliances that are insulated with cyclopentane-based foam, such as refrigerators and freezers, to be marked with cyclopentane warning labels due to its flammability.

[citation needed] Cyclopentane is a minor component of automobile fuel, with its share in US gasoline varying between 0.2 and 1.6% in early 1990s[8] and 0.1 to 1.7% in 2011.

[12][13] Cyclopentane requires safety precautions to prevent leakage and ignition as it is both highly flammable and can also cause respiratory arrest when inhaled.