Propadiene

Propadiene is the organic compound with the formula H₂C=C=CH₂. It is the simplest allene or compound with two adjacent C=C double bonds, and can also be identified as allene. 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 (or propyne), the mixture sometimes being called MAPD for methylacetylene-propadiene:

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 cracking propane to produce propene, an important feedstock in the chemical industry. MAPD interferes with the catalytic polymerization of propene.

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