Reaction of crotonaldehyde with various ethyl aluminum chlorides in methylene chloride. A 1H-NMR study

The reactions of crotonaldehyde (CA) with ethyl aluminum chlorides have been examined using a titration technique at low temperature. The titrations were followed by ¹H-NMR spectroscopy. Evidence for complexes of the type (Et₂AlCl)₂CA and (Et₂AlCl-CA)₂ has been obtained. Ethyl aluminum sesquichloride undergoes sequential addition of CA to the EtAlCl₂ moiety, to the Et₂AlCl moiety, and again to the EtAlCl₂ moiety. Ethyl aluminum dichloride undergoes ligand redistribution, alternately disproportionating and reproportionating, the ultimate product being EtAlCl₂-CA₂.