(a) Condensation reaction is a reaction whereby two molecules combine to form a single molecule. During this reaction, water is removed. For example, two amino acids combine by a covalent bond, water molecule is then removed as a second product. Esterification is a type of condensation reaction, whereby an ester is formed from an alcohol and a carboxylic acid. Another example of condensation reaction is saponification which describes the alkaline hydrolysis reaction of an ester.
(b) Addition reaction is a reaction whereby a double bond is broken by additing an element. Unsaturated organic molecules participate in addition reactions, this is because unsaturated organic molecules are those that have double bonds.
For example addition of hydrogen: Addition of hydrogen to a carbon-carbon double bond is called hydrogenation, which results in the removal of the double bond.
