Draw the structure of the product formed when 2-methylbutanal is treated with cold aqueous base.

When 2-methylbutnal is treated with base it looses its proton at alpha position as this proton is mildly acidic in nature and results in the formation of Enolate. The enolatae formed attacks on the carbonyl group of next aldehyde and forms a product called Aldol. Such reactions are called as Aldol Condensation. And those aldol condensation reactions in which the enolate and carbonyl group belongs to same carbonyl molecule like in our case, are called as Self Aldol Condensation reaction.