FOUR PRODUCTS ARE OBSERVED WHEN A CROSSED ALDOL IS ATTEMPTED USING TWO DIFFERENCE CARBONYL COMPOUNDS BOTH OF WHICH HAVE ALPHA HYDROGENS

q Note that there are two different enolates, that of acetaldehyde and that of propanal. Also, there are two different carbonyl compounds, ethanal and propanal. This gives rise to four possible products, all of which are observed. One of these products is the aldol of acetaldehyde with itself, one is that of propanal with itself, and the other two are cross aldols.