Saponification

the reaction of an ester with sodium hydroxide will hydrolyze the ester into a carboxylate salt and an alcohol

• this is a superior method since the formation of a carboxylate makes this reaction irreversible

this is the general reaction:

this reaction is irreversible because carboxylate salts are more stable than carboxylic acids and thus do not react under the same conditions

• this is a special case of LeChatelier’s Principle since one of the products is removed

mechanism of saponification:

“Saponification” itself means “making soap”

• it comes from the reaction of fats with bases to form soap

Fats and oils are triglycerides/triacylglycerols: triesters of glycerol

• when the triglycerides are hydrolyzed, sodium salts of the fatty acids are formed

  • these make soap an effective surfactant

  • they are amphipathic: having both polar and nonpolar regions

soap acts as a cleaning agent because it forms micelles: spherical structures formed by the self-assembly of amphipathic molecules

• these micelles can trap nonpolar dirt inside the nonpolar portions of the fatty acid salts