Butylenes

Butylenes is a traditional term used for a family of four-carbon hydrocarbons with the formula C4H8. In modern chemistry, it is often treated as synonymous with the butene group, referring mainly to open-chain alkenes of four carbons, though it can be used loosely to include related four-carbon isomers as well. The principal open-chain members are 1-butene, the cis and trans isomers of 2-butene, and 2-methylpropene (isobutene).

These compounds are generally volatile, flammable, and have low molecular weights. They are nonpolar, with limited water solubility and a tendency to be miscible with many organic solvents. Their physical state at room temperature varies: some behave as gases, while others are liquids.

Butylenes are produced during petroleum refining and petrochemical processing, particularly via cracking and dehydrogenation of larger hydrocarbons. They are important feedstocks in the manufacture of polymers and chemical intermediates. For example, 1-butene and other butene isomers are used as comonomers in polyethylene production to modify polymer properties. Isobutene is a key starting material for tert-butyl derivatives and certain fuel additives, such as MTBE.

Chemical reactions of butylenes center on the C=C double bond. They readily undergo addition reactions (hydrohalogenation, hydrogenation, halogenation) and participate in polymerization to form polybutenes and polyisobutylene, among other polymers. They can also undergo hydroformylation and other transformations that convert them into a variety of useful oxygenated and hydrocarbon products.

Safety and handling considerations reflect their flammability and volatility, with standard industrial precautions to prevent ignition and exposure.