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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)
Download
  • Molecular weight
    56.106
    g/mol
  • Content in air
    /

Critical Point

  • Temperature
    144.94
    °C
    292.892 °F 418.09 K
  • Pressure
    40.098
    bar
    4.0098E6 pa 581.5721 lbf/in2 39.5736 Atm 4009.8 Kpa 3.0076E4 mmHg
  • Density
    233.963
    kg/m³
    14.6058 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
    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
    2.684
    kg/m³
    1.6756E-1 lb/ft³
    2.684
    kg/m³
    1.6756E-1 lb/ft³
    2.684
    kg/m³
    1.6756E-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
    /
    /
    /
  • 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
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

at 1.013 bar and boiling point

m3(Volume)
kg(Mass)
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
C4H8
Isobutene

Safety

Information to safely use this molecule

  • Major hazards
  • Material compatibility
  • 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
      1.6
      vol/%
      1.6E4 ppm 1.6E4 ppm 1.6E-2 vol/vol
    • Upper flammability limit
      10
      vol/%
      10.E4 ppm 10.E4 ppm 0.1 vol/vol
  • 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
      1.8
      vol/%
      1.8E4 ppm 1.8E4 ppm 1.8E-2 vol/vol
    • Upper flammability limit
      9.6
      vol/%
      9.6E4 ppm 9.6E4 ppm 9.6E-2 vol/vol

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
    Satisfactory
  • Chloroprene
    Not recommended
    significant swelling
  • Chlorofluorocarbons
    Satisfactory
  • Silicon
    Not recommended
    significant swelling and modification of the properties of the material
  • Perfluoroelastomers
    Satisfactory
  • Fluoroelastomers
    Satisfactory
  • Nitrile rubber
    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.

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.