Answer 1

(a) It is a characteristic reaction of aldehydes and ketones containing active α – H atoms. The carbon atom adjacent to carbonyl carbon is called α –C and the H-atom attached to α –C is known as α – H atoms.
(b) When two moleccules of Aldehyde or Ketones containing active α – H atom are  warmed in presence of dilute base or dilute acid, they undergo self condensation to given β Hydroxy alde hyde (aldol) orβ Hydroxy ketone (ketol) resepctively. This reaction is known as aldol condensation. The Aldol or Ketol undergoes dehydration on heating to form unsaturated aldehyde or ketone.

Eg. Aldol condensation of Acetaldehyde

 

Step I : Addition

Step II : Condensation