Write structure formulae and names of four possible aldol condensation products form propanal and butanal. In each case. Indicate which aldehyde acts as nucleophile and which as electrophile.

Explanation

Both propanal and butanal have `prop`-hydrogen atoms present. These can undergo self aldol condensation as well as cross aldol condensation to give four compounds as follows :
(i) Condensation involving propanal. It is a case of self aldol condensation.