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Olefins and dienes

Isobutylene

Also known as Isobutene, 2-methylprop-1-ene, 2-Methylpropene

CAS 115-11-7Formula C4H8Molar mass 56.11 g/molEC 204-066-3
GHS signal word: Danger. Pictograms: Flammable, Gas under pressure 38 suppliers listed
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Isobutylene chemical structure, C4H8, CAS 115-11-7
2D chemical structure

Key facts

What buyers check first

All properties
Appearance
Colorless gas
Melting point
-140.7 °C
Boiling point
-7 °C
Density
0.589 g/cm³ at 25 °C (p >1 atm)
Flash point
-80 °C
HS code
290123
Category
Olefins and dienes
UN number
UN 1055
Illustrative photo, industrial gas cylinders secured with a safety chain in a warehouse
Typical packagingIllustrative packaging image, not the actual product

What is Isobutylene?

Plain description, key identifiers and synonyms

2-methylprop-1-ene is an alkene that is prop-1-ene substituted by a methyl group at position 2. It is a gas molecular entity and an alkene.

Identifiers

Registry numbers, names and line notations, tap to copy

IUPAC name
2-methylprop-1-ene
CAS number
115-11-7 CAS number cross-checkedOther or deprecated CAS: 42278-27-3
EC number
204-066-3
Molecular formula
C4H8
UNII
QA2LMR467H
MDL number
MFCD00008898
InChIKey
VQTUBCCKSQIDNK-UHFFFAOYSA-N
InChI
InChI=1S/C4H8/c1-4(2)3/h1H2,2-3H3
SMILES (canonical and isomeric)
CC(=C)C

Synonyms

  • Isobutene
  • 2-methylprop-1-ene
  • 2-Methylpropene
  • 2-Methyl-1-propene
  • 2-Methylpropylene
  • 1,1-Dimethylethylene
  • gamma-Butylene
  • 1-Propene, 2-methyl-
  • Isopropylidenemethylene
  • Propene, 2-methyl-
  • 1,1-Dimethylethene
  • 2-methyl propene
  • Methylpropene
  • iso-butene
  • iso-butylene
  • 2-Methyl-d3-propene
  • Isobutene (ca. 15% in Tetrahydrofuran)
  • Isobutene (ca. 9% in Hexane)
  • Isobutene (ca. 6% in Toluene)
  • 2-Methyl-d3-propene-3,3,3-d3
  • 2-methyl-1-propenhomopolymer
  • sym-Dimethylethylene
  • Polyisobutylene pound PIB pound(c)
  • i-butene
  • unsym. dimethylethylene
Show all 34 synonyms
  • isobutylene, various grades
  • Isobutene trimer
  • 2-methyl-l-propene
  • 2-methyl-2 propene
  • iso-C4H8
  • Polyisobutylene (1 g)
  • 2-Methylpropene, 99%
  • Propene, 2-methyl-, tetramer
  • 2-Methylpropene, purum, >=99.5%

Physical and chemical properties

Measured values and descriptors computed from the structure

Physical and chemical properties

Measured values, check the supplier specification for your grade

Appearance
Colorless gasexp.
Odour
Coal gas odorexp.
Melting point
-140.7 °Cexp.
Boiling point
-7 °Cexp.
Density
0.589 g/cm³ at 25 °C (p >1 atm)exp.
Flash point
-80 °Cexp.
Autoignition temperature
465 °Cexp.
Solubility
In water, 263 mg/L at 25 °Cexp.
Vapour pressure
2,308 mm Hg at 25 °Cexp.

Values vary by grade. Ask suppliers for the COA or TDS of the batch you buy.

Computed descriptors

Calculated from the structure, useful for screening and formulation

Molecular weight
56.11 g/molcalc.
Exact mass
56.0626 Dacalc.
LogP (octanol/water)
1.58calc.
Topological polar surface area
0 Ųcalc.
Hydrogen bond donors
0calc.
Hydrogen bond acceptors
0calc.
Rotatable bonds
0calc.
Heavy atoms
4calc.
Rings
0calc.
Aromatic rings
0calc.
Fraction sp3 carbons
0.5calc.
Formal charge
0calc.
Stereocentres
0calc.
Lipinski rule of five
Passes (0 violations)calc.

Calculated for screening. Confirm critical figures with the supplier.

Safety and hazards

GHS classification summary, not a safety data sheet

GHS signal word
Danger
GHS02: Flammable
Flammable
GHS04: Gas under pressure
Gas under pressure
421NFPA 704 rating

Hazard statements

  • H220Extremely flammable gas.
Precautionary statements (7)
  • P203Obtain, read and follow all safety instructions before use.
  • P210Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
  • P222Do not allow contact with air.
  • P280Wear protective gloves, protective clothing, eye protection and face protection.
  • P377Leaking gas fire: do not extinguish, unless leak can be stopped safely.
  • P381In case of leakage, eliminate all ignition sources.
  • P403Store in a well-ventilated place.
UN number
UN 1055
Transport hazard class
2.1

GHS classification summary, not a safety data sheet (SDS). Classifications can differ by supplier, grade and concentration. Always check the supplier's SDS.

Full safety data and first aid

Isobutylene suppliers

Sponsored listings first, then the documented ranking: membership, verification, replies, completeness, freshness and ratings

All 38 suppliers
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Where suppliers are based

38 suppliers in 7 countries

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Isobutylene price

Indicative price range per kg from live supplier offers

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Uses and applications

What the substance is used for, by industry and function

Primarily used to produce diisobutylene, trimers, butyl rubber, and other polymers, also to produce antioxidants for foods, packaging, food supplements, and for plastics.

Production of isooctane, high-octane aviation gasoline, butyl rubber, polyisobutene resins, tert-butyl chloride, tert-butanol methacrylates, copolymer resins with butadiene, acrylonitrile, etc., methyl-tert-butyl ether.

Isobutene is used as a monomer or the formation of a copolymer for the production of synthetic rubber and various plastics.

Industrial uses: Intermediate, Monomers, Fuel.

Consumer uses: Fuel, Intermediate.

How it is made

Obtained from refinery streams by absorption on 65% H2SO4 at about 15 °C, ... Separation from a mixed C4 stream using 50% H2SO4.

Isobutene is produced in refinery streams ... by reacting with an aliphatic primary alcohol and then hydrolyzing the resulting ether.

Fractionation of refinery gases, catalytic cracking of MTBE.

Regulatory status

Inventories, regulations and trade controls that list this substance

Europe

  • EU harmonised classification (CLP Annex VI)
    Index no: 601-012-00-4[3]

United States

  • TSCA inventory (USA)
    Status: Active in US commerce

HS code and trade data

Customs classification and reported world trade statistics

Global trade

World import and export statistics for the HS code Isobutylene is traded under.

HS 2901.23Indicative HS code

Butene (butylene) and isomers thereof

World exports in 2024
$683M
−8.1% vs 2023, imports $584M
2019 to 2024
Top exporters
  1. United States32.2%
  2. Belgium29.4%
  3. South Korea11.5%
Top importers
  1. Canada34.2%
  2. Thailand8.9%
  3. Germany7.7%
Reported customs values in USD, not prices.Full trade data

The HS code shown for Isobutylene is indicative (it was assigned by structure rules). Confirm the classification with your customs broker before shipping.

Frequently asked questions

Quick answers about Isobutylene, based on the data on this page

What is Isobutylene?

2-methylprop-1-ene is an alkene that is prop-1-ene substituted by a methyl group at position 2. It is a gas molecular entity and an alkene.

What is the CAS number of Isobutylene?

The CAS registry number of Isobutylene is 115-11-7. Other or deprecated CAS numbers: 42278-27-3.

What is the molecular formula and weight of Isobutylene?

The molecular formula of Isobutylene is C4H8 and its molar mass is 56.11 g/mol.

What is Isobutylene used for?

Primarily used to produce diisobutylene, trimers, butyl rubber, and other polymers, also to produce antioxidants for foods, packaging, food supplements, and for plastics.

Is Isobutylene hazardous?

Isobutylene carries the GHS signal word "Danger". Main hazards: extremely flammable gas. This summary is not an SDS, always read the supplier safety data sheet.

What is the HS code of Isobutylene?

Isobutylene is usually classified under HS code 290123 (Butene (butylene) and isomers thereof). This is indicative, confirm it with your customs broker before shipping.

Where can I buy Isobutylene?

CompoundList lists 38 suppliers of Isobutylene in United States, China, India, Japan and 3 more. Send one free request to get and compare quotes. Your contact details stay private until you accept a quote.

Where can I buy Isobutylene in India?

7 suppliers in India list Isobutylene on CompoundList. Filter the suppliers list by country and send a request to compare prices, grades and delivery times.

What is the price of Isobutylene?

Suppliers quote Isobutylene on request because prices depend on grade, purity, quantity and destination. A free request on CompoundList gets you several quotes to compare.

Guides for buyers

Practical guides that help when you source, ship or handle Isobutylene

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Data last updated 7 Oct 2026. Details may have changed, please confirm them with the supplier. Report an error on this page
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