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Propadiene

Names
Preferred IUPAC name Propadiene
Other names Allene Propadiene
Identifiers
CAS Number	463-49-0
3D model (JSmol)	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/h1-2H2Key: IYABWNGZIDDRAK-UHFFFAOYSA-N
SMILES C=C=C
Properties
Chemical formula	C3H4
Molar mass	40.065 g·mol
Appearance	Colorless gas
Melting point	−136 °C (−213 °F; 137 K)
Boiling point	−34 °C (−29 °F; 239 K)
log P	1.45
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H220
Precautionary statements	P210, P377, P381, P410+P403
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 , 100 kPa). Y verify (what is  ?) Infobox references

Propadiene (/proʊpəˈdaɪiːn/) or allene (/ˈæliːn/) 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. As a constituent of MAPP gas, it has been used as a fuel for specialized welding.

Production and equilibrium with methylacetylene

Propadiene exists in equilibrium with methylacetylene (propyne) and the mixture is sometimes called MAPD for methylacetylene-propadiene:

H₃CC≡CH ⇌ 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.

Occurrence in Space

In 2019 it was announced that propadiene had been detected in the atmosphere of Saturn's moon Titan using the NASA Infrared Telescope Facility. This was the first time that propadiene had been detected in space, and the second structural isomeric pair (paired with propyne) detected in Titan's atmosphere, after HCN-HNC.

References

1. ^ Favre, Henri A.; Powell, Warren H. (2014). Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. p. 375. doi:10.1039/9781849733069. 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, propadiene, is the preferred IUPAC name.
2. ^ 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
5. Lombardo, Nicholas A; Nixon, Conor A; Greathouse, Thomas K; Bézard, Bruno; Jolly, Antoine; Vinatier, Sandrine; Teanby, Nicholas A; Richter, Matthew J; G Irwin, Patrick J; Coustenis, Athena; Flasar, F Michael (2019-08-20). "Detection of Propadiene on Titan". The Astrophysical Journal Letters. 881 (2): L33. doi:10.3847/2041-8213/ab3860. ISSN 2041-8205.
6. Moreno, R.; Lellouch, E.; Lara, L. M.; Courtin, R.; Bockelée-Morvan, D.; Hartogh, P.; Rengel, M.; Biver, N.; Banaszkiewicz, M.; González, A. (December 2011). "First detection of hydrogen isocyanide (HNC) in Titan's atmosphere". Astronomy & Astrophysics. 536: L12. doi:10.1051/0004-6361/201118189. ISSN 0004-6361.
7. Hébrard, E.; Dobrijevic, M.; Loison, J. C.; Bergeat, A.; Hickson, K. M. (May 2012). "Neutral production of hydrogen isocyanide (HNC) and hydrogen cyanide (HCN) in Titan's upper atmosphere". Astronomy & Astrophysics. 541: A21. doi:10.1051/0004-6361/201218837. ISSN 0004-6361.

• Fuel gas
• Alkadienes