Propadiene

• Allen
• Dimethylenmethan

Colorless gas

Gaseous

-136 ° C

-34 ° C

0.91 MPa (21 ° C)

Insoluble in water

Attention

190.5 kJ / mol

Template: Infobox chemical / molecular formula search available

Propadiene [... the ː n] is the 1,2- diene of the propane, thus the parent compound of allenes. The trivial name of the connection is therefore also called " Allen". It has the molecular formula C3H4. The terminal CH2 groups lie with the central carbon atom in one plane but are rotated by 90 ° to each other. Chemical compounds in which one or more hydrogen atoms of the propadiene are replaced by other residues can be chiral ( axial chirality ).

Production and representation

The production is achieved in good yields in a synthetic sequence starting from the allyl bromide, which is first converted by addition of bromine to 1,2,3- tribromopropane. A subsequent dehydrohalogenation of 2,3- dibromopropene reduction with zinc powder gives propadiene.

Properties

Propadiene in the middle carbon atom is sp- hybridized, the two outer carbon atoms are sp2 - hybridized. One speaks here of cumulated double bonds.

Although propadiene as the related propene has double bonds, it does not show the typical chemical and physical characteristics of the alkenes. Takes place in the presence of basic catalysts such as isomerization to propyne.

Use

Propadiene is used in a mixture with propyne as welding and cutting gas. In the organic synthesis, it is used as a starting material in the preparation of insecticides.