(a) (i) The carbonyl group of aldehydes and ketones is reduced to CH2 group on treatment with zinc-amalgam and concentrated hydrochloric acid. The reaction is known as Clemmensen reduction
(ii) Carboxylic acids having an a-hydrogen are halogenated at the a-position on treatment with chlorine or bromine in the presence of small amount of red phosphorus to give a-halocarboxylic acids. This reaction is called ****–Volhard–Zelinsky reaction.
