Esters can be cleaved back into a carboxylic acid and an alcohol by reaction with water and a base. The reaction is called a saponification from the Latin sapo which means soap. The name comes from the fact that soap used to be made by the ester hydrolysis of fats. Due to the basic conditions a carboxylate ion is made rather than a carboxylic acid.
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Step 1: Nucleophilic attack by hydroxide  Step 2: Leaving group removal Step 3: Deprotonation Contributors
The objective of this laboratory is to make lye soap via the saponification reaction. Soap making has remained unchanged over the centuries. The ancient Roman tradition called for mixing rain water, potash and animal tallow (rendered form of beef or mutton fat). Making soap was a long and arduous process. First, the fat had to be rendered (melted and filtered). Then, potash solution was added. Since water and oil do not mix, this mixture had to be continuously stirred and heated sufficiently to keep the fat melted. Slowly, a chemical reaction called saponification would take place between the fat and the hydroxide which resulted in a liquid soap. When the fat and water no longer separated, the mixture was allowed to cool. At this point salt, such as sodium chloride, was added to separate the soap from the excess water. The soap came to the top, was skimmed off, and placed in wooden molds to cure. It was aged many months to allow the reaction to run to completion. All soap is made from fats and oils, mixed with alkaline (basic) solutions. There are many kinds of fats and oils, both animal and vegetable. Fats are usually solid at room temperature, but many oils are liquid at room temperature. Liquid cooking oils originate from corn, peanuts, olives, soybeans, and many other plants. For making soap, all different types of fats and oils can be used – anything from lard to exotic tropical plant oils. Saponification Reactions: \[\text{Fat} + \text{Lye} → \text{Soap} + \text{Glycerol}\] Be sure to exercise caution when dispensing the 9 M NaOH. If the chemical comes into contact with your skin, immediately rinse with water for a minimum of fifteen minutes and notify your instructor. Personal Protective Equipment (PPE) required: safety goggles, lab coat, closed-toe shoes
Materials: warm olive oil (preheated by instructor), 9 M sodium hydroxide solution, food coloring, assorted fragrances, stearic acid Equipment: tall 250 mL beaker, PLASTIC stirring rod, glass pipets and pipet bulbs
Experimental Observations You may make observations after the soap has dried; it will be returned in lab section or lecture.
Now rinse your hands thoroughly just in case your soap contains any unreacted sodium hydroxide. Questions
In order to continue enjoying our site, we ask that you confirm your identity as a human. Thank you very much for your cooperation. Saponification can be defined as a “hydration reaction where free hydroxide breaks the ester bonds between the fatty acids and glycerol of a triglyceride, resulting in free fatty acids and glycerol,” which are each soluble in aqueous solutions. From: Developments in Surface Contamination and Cleaning, 2015
Saponification is a process by which triglycerides are reacted with sodium or potassium hydroxide (lye) to produce glycerol and a fatty acid salt called "soap." The triglycerides are most often animal fats or vegetable oils. When sodium hydroxide is used, a hard soap is produced. Using potassium hydroxide results in a soft soap.
In saponification, a fat reacts with a base to form glycerol and soap. Todd Helmenstine Lipids that contain fatty acid ester linkages can undergo hydrolysis. This reaction is catalyzed by a strong acid or base. Saponification is the alkaline hydrolysis of the fatty acid esters. The mechanism of saponification is:
The chemical reaction between any fat and sodium hydroxide is a saponification reaction. triglyceride + sodium hydroxide (or potassium hydroxide) → glycerol + 3 soap molecules
Saponification is the chemical reaction that makes soap. Zara Ronchi / Getty Images While the one-step triglyceride reaction with lye is most frequently used, there is also a two-step saponification reaction. In the two-step reaction, steam hydrolysis of the triglyceride yields carboxylic acid (rather than its salt) and glycerol. In the second step of the process, alkali neutralizes the fatty acid to produce soap. The two-step process is slower, but the advantage of the process is that it allows for purification of the fatty acids and thus produces a higher quality soap. Saponification sometimes occurs in old oil paintings. Lonely Planet / Getty Images Saponification may result in both desirable and undesirable effects. The reactions sometimes damage oil paintings when heavy metals used in pigments react with free fatty acids (the "oil" in oil paint), forming soap. The reaction starts in the deep layers of a painting and works its way toward the surface. At present, there is no way to stop the process or identify what causes it to occur. The only effective restoration method is retouching. Wet chemical fire extinguishers use saponification to convert burning oils and fats into non-combustible soap. The chemical reaction further inhibits the fire because it is endothermic, absorbing heat from its surroundings and lowering the temperature of the flames. While sodium hydroxide hard soap and potassium hydroxide soft soap are used for everyday cleaning, there are soaps made using other metal hydroxides. Lithium soaps are used as lubricating greases. There are also "complex soaps" consisting of a mixture of metallic soaps. An example is a lithium and calcium soap.
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What happens during the saponification process?
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