Isobutene

C₄H₈
CAS Number 115-11-7
UN1012 (gas)

Molecule
Properties
Applications
Safety & Compatibility
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Liquid / Gas Volumes

Calculate the volume or mass of a quantity of gas or liquid

Liquid Phase

At boiling point at 1.013 bar

m³ (Volume)

kg (Mass)

Gas Phase

In standard conditions (1.013 bar, 15°C)

m³ (Volume)

kg (Mass)

Physical Properties

Download the set of data (XLS - 80.52 KB)

General Properties
Solid Phase
Liquid Phase
Gas Phase

Molecule phase diagram showing the transition phases between solid, liquid and gas as a function of temperature and pressure

Pressure (bar)

- Molar mass 56.106 g/mol
- Content in dry air /
Critical Point
- Temperature 144.75 °C
- Pressure 40 bar
- Density 234.75 kg/m³
Triple Point
- Temperature -140.75 °C
- Pressure 6.449E-6 bar

Pressure 1.013 bar

Latent heat of fusion (at melting point)	105.714 kJ/kg
Melting point	- 140.34 °C

Pressure 1.013 bar

Boiling point	- 7 °C
Latent heat of vaporization (at boiling point)	391.634 kJ/kg
Liquid density (at boiling point)	626.479 kg/m³

Pressure 1.013 bar

0 °C
15 °C
25 °C

Compressibility factor Z	9.6136E-1
Cp/Cv ratio γ	1.1329
Gas density (at boiling point)	2.683 kg/m³
Gas density	2.6032 kg/m³
Gas/(liquid at boiling point) equivalent	240.66 vol/vol
Heat capacity Cp	1.556 kJ/(kg.K)
Heat capacity Cv	1.3735 kJ/(kg.K)
Specific gravity	1.93
Specific volume	3.842E-1 m³/kg
Thermal conductivity	14.988 mW/(m.K)
Vapor pressure	1.324 bar
Viscosity	7.364E-5 Po

Compressibility factor Z	9.6845E-1
Cp/Cv ratio γ	1.1226
Gas density	2.4496 kg/m³
Gas/(liquid at boiling point) equivalent	255.75 vol/vol
Heat capacity Cp	1.5978 kJ/(kg.K)
Heat capacity Cv	1.4233 kJ/(kg.K)
Specific gravity	1.93
Specific volume	4.082E-1 m³/kg
Thermal conductivity	16.469 mW/(m.K)
Vapor pressure	2.221 bar
Viscosity	7.7972E-5 Po

Compressibility factor Z	9.7217E-1
Cp/Cv ratio γ	1.117
Gas density	2.3584 kg/m³
Gas/(liquid at boiling point) equivalent	265.64 vol/vol
Heat capacity Cp	1.629 kJ/(kg.K)
Heat capacity Cv	1.4584 kJ/(kg.K)
Specific gravity	1.93
Specific volume	4.24E-1 m³/kg
Thermal conductivity	17.494 mW/(m.K)
Vapor pressure	3.035 bar
Viscosity	8.0842E-5 Po

Applications

Examples of uses of this molecule in Industry and Healthcare

Chemicals

Isobutylene (or isobutene) is the feedstock for production of polybutene (butyl rubber). Isobutene is an intermediate in the manufacturing of methyl terbuthyl ether (MTBE).

Safety & Compatibility

Major Hazards
Material Compatibility

GHS02

Flammable

Autoignition Temperature, Flammability Limits & Flash Point

Europe (according to EN1839 for Limits and EN 14522 for autoignition temperature)

Autoignition temperature (Chemsafe)	465 °C
Lower flammability limit (IEC 80079-20-1)	1.6 vol%
Upper flammability limit (IEC 80079-20-1)	10 vol%

US (according to ASTM E681 for Limits and ASTM E659 for autoignition temperature)

Autoignition temperature (NFPA 325)	465 °C
Lower flammability limit (NFPA 325)	1.8 vol%
Upper flammability limit (NFPA 325)	9.6 vol%

Odor

Sweet

Metals

Aluminium	No data
Brass	No data
Monel	No data
Copper	No data
Ferritic Steel	No data
Stainless steel	No data
Zinc	No data
Titanium	No data

Plastics

Polytetrafluoroethylene	Satisfactory
Polychlorotrifluoroethylene	Satisfactory
Polyvinylidene fluoride	Satisfactory
Polyvinyl chloride	Significant swelling, change of mechanical properties Not recommended
Ethylene tetrafluoroethylene	No data
Polycarbonate	No data
Polyamide	Satisfactory
Polypropylene	Satisfactory

Elastomers

Butyl (isobutene- isoprene) rubber	Significant swelling and modification of the properties of the material Not recommended
Nitrile rubber	Satisfactory
Chloroprene	Significant swelling Not recommended
Chlorofluorocarbons	No data
Silicone	Significant swelling and modification of the properties of the material Not recommended
Perfluoroelastomers	Satisfactory
Fluoroelastomers	Satisfactory
Neoprene	No data
Polyurethane	Significant swelling, change of mechanical properties Not recommended
Ethylene-Propylene	Significant swelling and modification of the properties of the material Not recommended

Lubricants

Hydrocarbon based lubricant	Significant loss of mass Not recommended
Fluorocarbon based lubricant	Satisfactory

Materials compatibility

Recommendations : Air Liquide has gathered data on the compatibility of gases with materials to assist you in evaluating which materials to use for a gas system. Although the information has been compiled from what Air Liquide believes are reliable sources (International Standards: Compatibility of cylinder and valve materials with gas content; Part 1- Metallic materials: ISO11114-1 (March 2012), Part 2 - Non-metallic materials: ISO11114-2 (April 2013), it must be used with extreme caution and engineering judgement. No raw data such as these can cover all conditions of concentration, temperature, humidity, impurities and aeration. It is therefore recommended that this table is only used to identify possible materials for applications at high pressure and ambient temperature. Extensive investigation and testing under the specific conditions of use need to be carried out to validate a material selection for a given application. Contact the regional Air Liquide team for expertise service.

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More information

Isobutylene or 2-methylpropene is a hydrocarbon of industrial significance. Polymer and chemical grade isobutylene is typically obtained by dehydrating tertiary butyl alcohol or catalytic dehydrogenation of isobutane. Isobutylene is used as an intermediate in the production of a variety of products. It is also used in the production of oxygenated fuel. It is a colorless flammable gas.