Isobutene

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Isobutene

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C₄H₈

Isobutene

Physical Properties

Under solid (grey), liquid (blue) and vapor states (white) along the equilibrium curves

General properties
Solid phase
Liquid Phase
Gas Phase

(P)

log(P)

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Molecular weight

56.106
g/mol
Content in dry air

/

Critical Point

Temperature

144.75
°C
292.55 °F 417.9 K
Pressure

40
bar
4.E6 pa 580.1507 lbf/in2 39.4769 Atm 4000 Kpa 3.0003E4 mmHg
Density

234.75
kg/m³
14.6549 lb/ft³

Triple Point

Temperature

- 140.75
°C
- 221.35 °F 132.4 K
Pressure

6.449E-6
bar
6.449E-1 pa 9.3535E-5 lbf/in2 6.3647E-6 Atm 6.449E-4 Kpa 4.8372E-3 mmHg

Pressure 1.013 bar

Melting point

- 140.34
°C
- 220.612 °F 132.81 K
Latent heat of fusion (at melting point)

105.714
kJ/kg
45.4793 Btu/lb 25.2663 kcal/kg
Solid density

/

Pressure 1.013 bar

Liquid density (at boiling point)

626.479
kg/m³
39.1097 lb/ft³
Boiling point

- 7
°C
19.4 °F 266.15 K
Latent heat of vaporization (at boiling point)

391.634
kJ/kg
168.4853 Btu/lb 93.6028 kcal/kg

Pressure1.013barTemperature

Compressibility factor Z

9.6136E-1

9.6845E-1

9.7217E-1
Cp/Cv ratio γ

1.1329

1.1226

1.117
Dynamic viscosity

7.364E-5
Po
7.364 µPa.s 7.364E-6 PA.S 4.9484E-6 lb/ft/s

7.7972E-5
Po
7.7972 µPa.s 7.7972E-6 PA.S 5.2395E-6 lb/ft/s

8.0842E-5
Po
8.0842 µPa.s 8.0842E-6 PA.S 5.4323E-6 lb/ft/s
Gas density at boiling point

2.683
kg/m³
1.6749E-1 lb/ft³

2.683
kg/m³
1.6749E-1 lb/ft³

2.683
kg/m³
1.6749E-1 lb/ft³
Gas density

2.6032
kg/m³
1.6251E-1 lb/ft³

2.4496
kg/m³
1.5292E-1 lb/ft³

2.3584
kg/m³
1.4723E-1 lb/ft³
Heat capacity at constant pressure Cp

1.556
kJ/(kg.K)
3.7189E-1 BTU/lb∙°F 1556 J/kg∙K 3.7189E-1 kcal/kg∙K

1.5978
kJ/(kg.K)
3.8188E-1 BTU/lb∙°F 1597.8 J/kg∙K 3.8188E-1 kcal/kg∙K

1.629
kJ/(kg.K)
3.8934E-1 BTU/lb∙°F 1629 J/kg∙K 3.8934E-1 kcal/kg∙K
Heat capacity at constant volume Cv

1.3735
kJ/(kg.K)
3.2827E-1 BTU/lb∙°F 1373.5 J/kg∙K 3.2827E-1 kcal/kg∙K

1.4233
kJ/(kg.K)
3.4018E-1 BTU/lb∙°F 1423.3 J/kg∙K 3.4018E-1 kcal/kg∙K

1.4584
kJ/(kg.K)
3.4857E-1 BTU/lb∙°F 1458.4 J/kg∙K 3.4857E-1 kcal/kg∙K
Liquid (at boiling point)/gas equivalent

240.66
mol/mol

255.75
mol/mol

265.64
mol/mol
Solubility in water

/

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Specific gravity

1.93

1.93

1.93
Specific volume

3.842E-1
m³/kg
6.1543 ft³/lb

4.082E-1
m³/kg
6.5387 ft³/lb

4.24E-1
m³/kg
6.7918 ft³/lb
Thermal conductivity

14.988
mW/m∙K
8.6657E-3 Btu/ft/h/°F 1.2896E-1 cal/hour∙cm∙°C 3.5822E-5 cal/s∙cm∙°C 1.4988E-2 W/(m∙K)

16.469
mW/m∙K
9.522E-3 Btu/ft/h/°F 1.417E-1 cal/hour∙cm∙°C 3.9362E-5 cal/s∙cm∙°C 1.6469E-2 W/(m∙K)

17.494
mW/m∙K
1.0115E-2 Btu/ft/h/°F 1.5052E-1 cal/hour∙cm∙°C 4.1812E-5 cal/s∙cm∙°C 1.7494E-2 W/(m∙K)
Vapor pressure

1.324
bar
1.324E5 pa 19.203 lbf/in2 1.3067 Atm 132.4 Kpa 993.0844 mmHg

2.221
bar
2.221E5 pa 32.2129 lbf/in2 2.192 Atm 222.1 Kpa 1665.8916 mmHg

3.035
bar
3.035E5 pa 44.0189 lbf/in2 2.9953 Atm 303.5 Kpa 2276.4435 mmHg

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C₄H₈

Isobutene

Liquid / Gas Volumes

Calculate a liquid or gas volume or a mass

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)

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C₄H₈

Isobutene

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).

Chemicals

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C₄H₈

Isobutene

Safety & Compatibility

Information to safely use this molecule

Major hazards
Material compatibility

Safety

GHS02

Flammable

Autoignition Temperature in Air at Patm and Flammability Limits in Air at Patm and 293.15 K (except if the temperature is indicated)

Europe (according to EN1839 for Limits and EN 14522 for autoignition temperature)
- Auto-ignition temperature
  
  465
  °C
  869 °F 738.15 K
- Flash point
  
  /
- Lower flammability limit
  
  /
- Upper flammability limit
  
  /
US (according to NFPA for Limits and ASTM E659 for autoignition temperature)
- Auto-ignition temperature
  
  465
  °C
  869 °F 738.15 K
- Flash point
  
  /
- Lower flammability limit
  
  /
- Upper flammability limit
  
  /

Odor

Sweet

Metals

Aluminium

Satisfactory
Brass

Satisfactory
Monel

Satisfactory
Copper

Satisfactory
Ferritic Steel

Satisfactory
Stainless steel

Satisfactory
Zinc

No data
Titanium

No data

Plastics

Polytetrafluoroethylene

Satisfactory
Polychlorotrifluoroethylene

Satisfactory
Polyvinylidene fluoride

Satisfactory
Polyvinyl chloride

Satisfactory
Ethylene tetrafluoroethylene

Satisfactory
Polycarbonate

No data
Polyamide

Satisfactory
Polypropylene

Satisfactory

Elastomers

Buthyl (isobutene- isoprene) rubber

Not recommended
significant swelling
Nitrile rubber NBR

Satisfactory
Chloroprene

Not recommended
significant swelling
Silicone

Not recommended
significant swelling and modification of the properties of the material
Perfluoroelastomers

Satisfactory
Fluoroelastomers

Satisfactory
Neoprene

Satisfactory
Polyurethane

No data
Ethylene-Propylene

Not recommended
significant swelling and modification of the properties of the material

Lubricants

Hydrocarbon based lubricant

Not recommended
significant loss of mass
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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C₄H₈

Isobutene

Learn More

General information

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.