SCCH121 EXPERIMENT 3 2015v2.0 Page 2 BACKGROUND Saponification When an ester is hydrolysed in the presence of a base, the reaction is called saponification. The products are the salt of the carboxylic acid and the alcohol. Although the ester is usually insoluble in water, the salt and alcohol (if short chain) are soluble. O O ____CH3—C—O—CH2CH3+ NaOH oCH3—C—O—Na++ HO—CH2CH3ethyl acetate sodium acetate ethanol Saponification: preparation of soap For centuries soap has been made from animal fats and lye (NaOH), which was obtained by pouring water through wood ashes. The hydrolysis of a fat or oil by a base such as NaOH is called saponificationand the salts of the fatty acids obtained are called soaps. The other product of hydrolysis is glycerol, which is soluble in water. The soap is precipitated out by the addition of saturated NaCl solution called brine. + NaOH o3 + Tripalmittin lye sodium palmitate free glycerol The fats that are most commonly used to make soap are lard and tallow from animal fat and coconut, palm and olive oils from vegetables. Castile soap is made from olive oil. Soaps that float have air pockets. Soft soaps are made from KOH instead of NaOH to give potassium salts.