Isobutylene

Description

Isobutylene (2-methylpropene)

Isobutylene is a simple unsaturated hydrocarbon, an alkene that is widely used in industry. Below is a concise overview.

Key details

• Chemical formula: C4H8
• IUPAC name: 2-methylpropene
• Common names: isobutene, isobutylene
• Structure: CH2=C(CH3)2 (a terminal double bond on a branched propene skeleton)

Properties (at room temperature)

• Physical state: Colorless gas (liquefies under modest pressure)
• Boiling point: around -6.9 °C
• Odor: Generally mild, not distinctive
• Flammability: Highly flammable
• Reactivity: Reactive across the carbon–carbon double bond; participates in many addition and polymerization reactions

Production and sources

• Primarily produced by dehydration of tert-butanol (acid-catalyzed reaction)
• Can also arise as a byproduct in petrochemical processes and refinery streams

Major uses

• Monomer for polyisobutylene (PIB): Used in sealants, adhesives, lubricants, and some tire materials
• Feedstock for tert-butyl alcohol hydration: Hydration of isobutylene yields tert-butanol
• Fuel additives and chemical intermediates: Reacts with methanol to form MTBE (methyl tert-butyl ether) in gasoline production
• Other chemical syntheses often utilize its reactive double bond for halogenation, hydrohalogenation, and polymerization

Reactions to know

• Electrophilic addition across the double bond (for example, HBr adds to form tert-butyl bromide by Markovnikov rule)
• Hydration to tert-butanol under acidic catalysis
• Polymerization to polyisobutylene with suitable catalysts
• Halogenation and oxyfunctionalization as part of organic synthesis

Safety and handling

• Hazards: Flammable gas, forms explosive mixtures with air
• Storage: In well ventilated areas, away from heat, sparks, and oxidizers; stored under pressure as appropriate
• Stabilization: Polymerization inhibitors (for example, tert-butyl catechol or similar stabilizers) are used in transport and storage
• Handling tips: Use closed systems, appropriate ventilation, and PPE as indicated by your site safety guidelines

Quick comparison (one glance)

• Isobutylene vs Ethylene: Isobutylene is a branched C4H8 alkene with a higher molecular weight and different reactivity due to the methyl groups, while ethylene is a smaller, linear C2H4 alkene.
• Isobutylene vs Isobutane: Isobutylene has a double bond (reactive site) whereas isobutane is fully saturated (no double bonds) and is a gas at room temperature.

Summary

Isobutylene is a versatile C4H8 alkene used primarily as a monomer for polyisobutylene and as a feedstock in MTBE production. It is a flammable gas handled under controlled conditions, with reactivity centered on its double bond.

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