1) Butene 2) Butylene 
Isobutylene (or 2-methylpropene) is a hydrocarbon of industrial significance. It is a four-carbon branched alkene (olefin), one of the four isomers of butylene. At standard temperature and pressure it is a colorless flammable gas. ==Uses== Isobutylene is used as an intermediate in the production of a variety of products. It is reacted with methano...
(from the article `butene`) ...compounds belonging to the series of olefinic hydrocarbons. The chemical formula is C4H8. The isomeric forms are 1-butene, cis-2-butene, ...
[n] - used also in making gasoline components