|Molecular formula||C 3 H 4|
|External identifiers / databases|
|Molar mass||40.06 g mol −1|
−136 ° C
−34 ° C
0.91 M Pa (21 ° C)
almost insoluble in water
|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.
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
- entry on all. In: Römpp Online . Georg Thieme Verlag, accessed on September 29, 2014.
- Allene data sheet at Sigma-Aldrich , accessed on April 22, 2011 ( PDF ).
- 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.
- Hauptmann / Graefe / Remane: Textbook of Organic Chemistry , Deutscher Verlag der Grundstoffindustrie, Leipzig, 1980, p. 230.
- Norbert Krause (editor), A. Stephen K. Hashmi (editor): Modern Allene Chemistry , Wiley-VCH Verlag, 2004. ISBN 978-3-527-30671-8 .