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Structural formula
Structural formula of propadiene
Surname Propadien
other names
  • Everyone
  • Dimethylene methane
  • Propa-1,2-diene
Molecular formula C 3 H 4
Brief description

colorless gas

External identifiers / databases
CAS number 463-49-0
EC number 207-335-3
ECHA InfoCard 100.006.670
PubChem 10037
Wikidata Q422942
Molar mass 40.06 g mol −1
Physical state


Melting point

−136 ° C

boiling point

−34 ° C

Vapor pressure

0.91 M Pa (21 ° C)


almost insoluble in water

safety instructions
GHS labeling of hazardous substances
02 - Highly / extremely flammable 04 - gas bottle


H and P phrases H: 220-280
P: 210-377-381-410 + 403
Thermodynamic properties
ΔH f 0

190.5 kJ / mol

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Propadiene [ … diˈeːn ] is the 1,2- diene of propane and thus the parent compound of the allenes . The common name of the connection is therefore "Allen" . It has the molecular formula C 3 H 4 . The terminal CH 2 groups are in one plane with the middle C atom, but are rotated by 90 ° with respect to one another. Chemical compounds in which one or more hydrogen atoms of propadiene have been exchanged for other radicals can be chiral ( axial chirality ).

Extraction and presentation

The preparation succeeds in good yields in a synthesis sequence starting from allyl bromide , which is first converted to 1,2,3-tribromopropane by bromine addition. Subsequent dehydrohalogenation to 2,3-dibromopropene and reduction using zinc powder gives the propadiene.

Synthesis of Propadiene


In propadiene, the middle carbon atom is sp-hybridized, the two outer carbon atoms are sp 2 - hybridized . One speaks here of cumulative double bonds .

Although propadiene, like its related propene, has double bonds, it does not display the typical chemical and physical properties of alkenes . For example, in the presence of basic catalysts, isomerization to propyne takes place .

H 2 C = C = CH 2 ⇌ H 3 C − C≡CH


Propadiene is used in a mixture with propyne as welding and cutting gas ( MAPP gas ). In organic synthesis, it is used as a raw material in the manufacture of insecticides .

Web links

Commons : Allene  - collection of images, videos and audio files

Individual evidence

  1. a b c d entry on all. In: Römpp Online . Georg Thieme Verlag, accessed on September 29, 2014.
  2. a b c Allene data sheet at Sigma-Aldrich , accessed on April 22, 2011 ( PDF ).
  3. a b Entry on all in the GESTIS substance database of the IFA , accessed on January 9, 2019(JavaScript required) .
  4. David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-23.
  5. Hauptmann / Graefe / Remane: Textbook of Organic Chemistry , Deutscher Verlag der Grundstoffindustrie, Leipzig, 1980, p. 230.
  6. ^ Norbert Krause (editor), A. Stephen K. Hashmi (editor): Modern Allene Chemistry , Wiley-VCH Verlag, 2004. ISBN 978-3-527-30671-8 .