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Propadiene

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Propadiene
Stereo structural formula of propadiene with explicit hydrogens
Stereo structural formula of propadiene with explicit hydrogens
Spacefill model of propadiene
Spacefill model of propadiene
Ball and stick model of propadiene
Names
IUPAC name
Allene
Systematic IUPAC name
Propa-1,2-diene (substitutive)
Dimethylenecarbon,
dimethylenemethane (additive)
Identifiers
3D model (JSmol)
1730774
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.006.670 Edit this at Wikidata
EC Number
  • 207-335-3
860
MeSH Propadiene
UN number 2200
  • InChI=1S/C3H4/c1-3-2/h1-2H2 checkY
    Key: IYABWNGZIDDRAK-UHFFFAOYSA-N checkY
  • C=C=C
  • C(=C)=C
Properties
C3H4
Molar mass 40.065 g·mol−1
Appearance Colorless gas
Melting point −136 °C (−213 °F; 137 K)
Boiling point −34 °C (−29 °F; 239 K)
log P 1.45
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideFlammability 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 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g. hydrogen peroxideSpecial hazards (white): no code
0
4
3
Explosive limits 13%
Safety data sheet (SDS) External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Propadiene is the organic compound with the formula H2C=C=CH2. It is the simplest allene or compound with two adjacent C=C double bonds, and can also be identified as allene.[1] As a constituent of MAPP gas, it has been used as a fuel for specialized welding.

Production and equilibrium with methylacetylene

Allene exists in equilibrium with methylacetylene (or propyne), the mixture sometimes being called MAPD for methylacetylene-propadiene:

H3CC≡CH ⇌ H2C=C=CH2

for which Keq = 0.22 at 270 °C or 0.1 at 5 °C. MAPD is produced as a side product, often an undesirable one, of cracking propane to produce propene, an important feedstock in the chemical industry. MAPD interferes with the catalytic polymerization of propene.[2]

References

  1. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "allenes". doi:10.1351/goldbook.A00238
  2. ^ Klaus Buckl, Andreas Meiswinkel "Propyne" in Ullmann's Encyclopedia of Industrial Chemistry 2008, Wiley-VCH, Weinheim. doi:10.1002/14356007.m22_m01


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