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(also butenes), unsaturated hydrocarbons, C4H8; colorless gases. Three structural isomers of butylene are known: namely, normal α-butylene (1-butene), CH2=CH—CH2—CH3; normal β-butylene (2-butene or pseudobutylene), CH3—CH=CH—CH3, which exists in trans- and cis- forms; and isobutylene, (CH3)2C=CH2. The three isomers have boiling points of -6.25° C, 1.0°-3.72° C, and -6.90° C, respectively.
Butylenes are readily soluble in many organic solvents and poorly soluble in water. They possess all the characteristics of alkenes. Mixtures of air and butylene containing 1.7-9 percent butene are explosive. In industry, butylènes are isolated from the butane-butylene fraction of gases in petroleum refining or are obtained synthetically by the catalytic dehydration of butyl alcohols. Butylenes are used to obtain butadiene, butyl rubber, polyisobutylene (Oppanol), isooctane, lubricating oils, and other products.