Propadiene

Propadiene
Stereo structural formula of propadiene with explicit hydrogens	Spacefill model of propadiene
Names
	Preferred IUPAC name Propa-1,2-diene
	Other names Allene; Propadiene
Identifiers
CAS Number	463-49-0 ;
3D model (JSmol)	Interactive image; Interactive image;
Beilstein Reference	1730774
ChEBI	CHEBI:37601 ;
ChEMBL	ChEMBL116960 ;
ChemSpider	9642 ;
ECHA InfoCard	100.006.670
EC Number	207-335-3;
Gmelin Reference	860
MeSH	Propadiene
PubChem CID	10037;
UNII	4AV0LZ8QKB ;
UN number	2200
CompTox Dashboard (EPA)	DTXSID1029178 ;
	InChI InChI=1S/C3H4/c1-3-2/h1-2H2 Key: IYABWNGZIDDRAK-UHFFFAOYSA-N ;
	SMILES C=C=C; C(=C)=C;
Properties
Chemical formula	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)	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). verify (what is ?) Infobox references

Propadiene or allene 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.^[2] 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 (propyne) and the mixture is sometimes called MAPD for methylacetylene-propadiene:

H₃CC≡CH

{\ce {<<=>}}

H₂C=C=CH₂

for which K_eq = 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.^[3]

References

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

[iupac2013-1] 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] IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "allenes". doi:10.1351/goldbook.A00238

[3] 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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