2-methylpropene, also known as isobutylene or isobutene, is a hydrocarbon with the chemical formula C4H8. Its molar mass is 56.11 grams per mol and its density is 0.5879 grams per cubic centimeter. It is a colorless gas at standard temperature and pressure, and it is insoluble in water.
Isobutylene has a range of industrial uses. For example, it is used to produce isooctane, a fuel additive, by reacting with butane. It can also be polymerized to produce polyisobutylene, a type of synthetic rubber. Isobutylene is industrially produced from the catalytic dehydrogenation of isobutane or from the dehydration of tertiary butyl alcohol. It is classified as a hazardous substance due to its high flammability and ability to cause explosions.