Propadiene

Propadiene (/prpəˈdn/) or allene (/ˈæln/) is the organic compound with the formula H2C=C=CH2. It is the simplest allene i.e. a compound with two adjacent carbon double bonds.[3] As a constituent of MAPP gas, it has been used as a fuel for specialized welding.

Propadiene
Stereo structural formula of propadiene with explicit hydrogens
Spacefill model of propadiene
Ball and stick model of propadiene
Names
Preferred IUPAC name
Propa-1,2-diene[1]
Other names
Allene[1]
Propadiene
Identifiers
  • 463-49-0 checkY
3D model (JSmol)
1730774
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.006.670 Edit this at Wikidata
EC Number
  • 207-335-3
860
MeSH Propadiene
UNII
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
Safety data sheet External MSDS
GHS pictograms GHS02: Flammable GHS04: Compressed Gas[2]
GHS Signal word Danger
H220, H280[2]
P210, P377, P381, P410+403[2]
NFPA 704 (fire diamond)
0
4
3
Explosive limits 13%
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 ?)
Infobox references

Production and equilibrium with methylacetyleneEdit

Allene exists in equilibrium with methylacetylene (propyne) and the mixture is sometimes 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 dehydrogenation of propane to produce propene, an important feedstock in the chemical industry. MAPD interferes with the catalytic polymerization of propene.[4]

ReferencesEdit

  1. ^ a b Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 375. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4. The name allene, for CH2=C=CH2, is retained for general nomenclature only; substitution is allowed, but not by alkyl or any other group that extends the carbon chain, nor characteristic groups expressed by suffixes. The systematic name, propa-1,2-diene, is the preferred IUPAC name.
  2. ^ a b c Record of Allene in the GESTIS Substance Database of the Institute for Occupational Safety and Health, accessed on 17 November 2020.
  3. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "allenes". doi:10.1351/goldbook.A00238
  4. ^ Klaus Buckl, Andreas Meiswinkel "Propyne" in Ullmann's Encyclopedia of Industrial Chemistry, 2008, Wiley-VCH, Weinheim. doi:10.1002/14356007.m22_m01