Which of the following fatty acids does NOT form soap?

 Butyric acid is not used to form a soap. • Soaps are the metallic salts of fatty acids and Sodium (Na) & Potassium (K) are the commonly used salts. • RCOO^-  Na⁺ or RCOO^- K⁺ is the general formula of soaps where R is the alkyl group of the parent fatty acid. • Palmitic acid, Stearic acid, Oleic acid, Lauric acid, and Myristic acid are used to prepare soaps. • The metallic ion is the hydrophilic (water-loving) part and the organic chain is the lipophilic (oil/fat- loving) part.