Isobutylene

Isobutylene, also known as isobutene or 2-methylpropene, is an unsaturated hydrocarbon with the formula C4H8. It is an alkene characterized by a terminal double bond, giving the structure CH2=C(CH3)2. The compound is a colorless gas at room temperature that can be stored as a liquefied gas under pressure or at low temperatures.

Industrial production and uses

Isobutylene is produced commercially by dehydration of tert-butanol or as a byproduct of certain refinery and cracking processes. It serves as a key feedstock in several large-scale applications. A major use is in the production of polyisobutylene (PIB) via cationic polymerization, a polymer employed in sealants, lubricants, and tire inner layers, among other functions. Isobutylene is also a precursor to gasoline oxygenates such as methyl tert-butyl ether (MTBE) and tert-amyl methyl ether (TAME), which have been used to improve octane ratings and reduce emissions.

Reactivity and handling

As an alkene, isobutylene readily undergoes electrophilic addition reactions and polymerization. In industry, polymerization is controlled using inhibitors to prevent premature polymerization during storage and transport. The compound is highly flammable and should be handled with appropriate ventilation and standard precautions for handling volatile organic compounds.

Safety and terminology

Common synonyms include isobutene and 2-methylpropene. It is typically discussed in the context of its role as a reactive monomer for PIB production and as a precursor to gasoline additives, reflecting its broad industrial relevance.