Final answer:
In a saponification reaction, the ester functional group is hydrolyzed, resulting in the formation of soap molecules, which consist of alcohol and the sodium or potassium salts of fatty acids.
Step-by-step explanation:
Saponification Reaction Functional Group
The organic functional group that is hydrolyzed in a saponification reaction is the ester group. During saponification, triglycerides, which are esters, undergo the process of alkaline hydrolysis, where a strong base like sodium hydroxide (NaOH) or potassium hydroxide (KOH) breaks the ester bond. This results in the formation of an alcohol, such as glycerol, and the sodium or potassium salts of fatty acids, which are the soap molecules. Notably, the soap molecules contain a nonpolar hydrocarbon end and an ionic end known as the carboxylate group. Thus, in the context of making soap, saponification specifically refers to the hydrolysis of long-chain fatty acid esters to produce these carboxylate salts of fatty acids.