1,3-Butadienal, also called vinylketene, is an organic compound and the simplest vinylketene. Like other vinylketenes, it occurs primarily as a reactive intermediate in cycloaddition reactions.
As a vinylketene not protected by steric effects, 1,3-butadienal is typically prepared in situ. Dehydrohalogenation of vinyl acyl chlorides produces vinylketene:
The molecule was first properly observed in pyrolysis of the ynol ether ethoxybutenyne, a retro-ene reaction:
An analogous decomposition of yields ethenone. The compound also occurs from the radical addition of the allyl and radicals, a potential side reaction in the production of allyl radicals from propene and oxalyl chloride. As a reaction intermediate, it is produced from electrocyclic ring-opening of cyclobutenone.