H H C C H C H H C C H C H C) Reactions involving – COOH group ) Reduction i) Partial reduction to alcohols Carboxylic acids are reduced to primary alcohols by LiAlH or with hydrogen in the presence of copper chromite as catalyst. Sodium borohydride does not reduce the – COOH group. Example CH CH OH + H O LiAlH ethanoicacid ethanol (H) ii) Complete reduction to alkanes When treated with HI and red phosphorous, carboxylic acid undergoes complete reduction to yield alkanes containing the same number of carbon atoms. Example OH + HI Red P CH + 3I + 2H O Acetic acid Ethane K XII U12-Carbonyl XII U12-Carbonyl - - - - ) Decarboxylation Removal of CO from carboxyl group is called as decarboxylation.
Carboxylic acids lose carbon di oxide to form hydrocarbon when their sodium salts are heated with soda lime (NaOH and CaO in the ratio : ) Example ONa + NaOH CH + Na CO Sodium acetate Methane CaO ) Kolbe’s electrolytic decarboxylation The aqueous solutions of sodium or potassium salts of carboxylic acid on electrolysis gives alkanes at anode. This reaction is called kolbes electrolysis. CH COONa CH COONa + 2CO + 2Na Electrolysis Sodium acetate Anode Cathode Sodium formate solution on electrolysis gives hydrogen ) Reactions with ammonia Carboxylic acids react with ammonia to form ammonium salt which on further heating at high temperature gives amides. Example OH + NH NH NH H O Acetic acid Ammonium acetate Acetamide ) Action of heat in the presence of P O Carboxylic acid on heating in the presence of a strong dehydrating agent such as P O forms acid anhydride.
Example P O + H O Acetic acid Acetic anhydride XII U12-Carbonyl XII U12-Carbonyl - - - - D) Substitution reactions in the