Isobutylene

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Isobutylene
Skeletal formula of isobutylene
Ball-and-stick model of isobutylene
Ball-and-stick model of isobutylene
Space-filling model of isobutylene
Space-filling model of isobutylene
Names
Preferred IUPAC name
2-Methylprop-1-ene
Other names
2-Methylpropene
Isobutene
γ-Butylene
2-Methylpropylene
Methylpropene
Identifiers
3D model (
JSmol
)
ChEBI
ChemSpider
ECHA InfoCard
 100.003.697 Edit this at Wikidata
EC Number
  • 204-066-3
RTECS number
  • UD0890000
UNII
UN number
1075
  • InChI=1S/C4H8/c1-4(2)3/h1H2,2-3H3 checkY
    Key: VQTUBCCKSQIDNK-UHFFFAOYSA-N checkY
  • InChI=1/C4H8/c1-4(2)3/h1H2,2-3H3
  • CC(=C)C
Properties[1]
C4H8
Molar mass 56.106 g/mol
Appearance Colorless gas
Density 0.5879 g/cm3, liquid
Melting point −140.3 °C (−220.5 °F; 132.8 K)
Boiling point −6.9 °C (19.6 °F; 266.2 K)
-44.4·10−6 cm3/mol
Hazards[2]
GHS labelling:
Flam. Gas 1Press. Gas
Danger
H220
P210, P377, P381, P403
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
4
0
Flash point flammable gas
465 °C (869 °F; 738 K)
Explosive limits
 1.8–9.6%
Related compounds
Related butenes
trans-2-Butene
Related compounds
 Isobutane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Isobutylene (or 2-methylpropene) is a

isomers of butylene. It is a colorless flammable gas, and is of considerable industrial value.[3]

Production

Polymer and chemical grade isobutylene is typically obtained by dehydrating

tertiary butyl alcohol (TBA) or catalytic dehydrogenation of isobutane (Catofin or similar processes).[4] Gasoline additives methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE), respectively, are produced by reacting methanol or ethanol
with isobutylene contained in butene streams from olefin steam crackers or refineries, or with isobutylene from dehydrated TBA. Isobutylene is not isolated from the olefin or refinery butene stream before the reaction, as separating the ethers from the remaining butenes is simpler. Isobutylene can also be produced in high purities by "back-cracking" MTBE or ETBE at high temperatures and then separating the isobutylene by distillation from methanol.

Isobutylene is a byproduct in the ethenolysis of diisobutylene to prepare neohexene:[5]

(CH3)3C-CH=C(CH3)2 + CH2=CH2 → (CH3)3C-CH=CH2 + (CH3)2C=CH2

Uses

Isobutylene is used in the production of a variety of products. It is alkylated with butane to produce

Friedel-Crafts alkylation of phenols
with isobutylene.

catalysts:[6]

NH3 + CH2=C(CH3)2 → H2NC(CH3)3

Applications are found in the calibration of photoionization detectors.

Safety

Isobutylene is a highly flammable gas.

See also

References

  1. ISBN 091191028X
    , 5024.
  2. ^ Isobutene, International Chemical Safety Card 1027, Geneva: International Programme on Chemical Safety, April 2000
  3. ISBN 978-3527306732
    .
  4. ISBN 978-0-471-41782-8
    .
  5. ^ Lionel Delaude; Alfred F. Noels. "Metathesis". Kirk-Othmer Encyclopedia of Chemical Technology. Wiley.
  6. ISBN 978-3527306732
    .

External links
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