Saponification:

 

Abstract:

The purpose of this experiment is to obtain solid soap. How?

By making a reaction between sodium hydroxide (NaOH) and olive oil.

 

Introduction:

Lipids are organic molecules which have similar solubility properties. They are not soluble in water, but they are soluble in organic solvents.

They are mainly made of carbon and hydrogen atoms linked to each other with covalent bonds poorly polar.

Lipids can lead to a saponification reaction, a reaction which consists in the basic hydrolysis of esters, therefore represents in fact an irreversible acidic nucleophilic substitution reaction, which leads to the consumption of one mole of NaOH for one mole of ester.

 

 

Materials:

Instrumentation: techical balance, heating plate, thermometers, mixer;.

Glassware: pyrex glass containers resistant to heat and corrosion, glass pipets, steel spatula, glass rod, plastic containers (moulds), plastic boats, water containers, beaker;.

Substances:

-500 g olive oil

-62,5 g NaOH (hydroxide sodium) by drop

-150 g distilled water

-10 ml essential oil

-colorants

 

PPE: smock, isolating gloves, protective glasses.

 

PROCEDURE:

1. Wear the PPE;
2. Place the thermometers in the appropriate supports and fill the plastic tray with cold water (here the sodium hydroxide and distilled water solution will be cooled);
3. Weigh the sodium hydroxide with the aid of the balance and the plastic boats, take the required amount of distilled water and place it in a 500ml beaker, then proceed by inserting the olive oil inside the 1L beaker;
4. Gradually pour the sodium hydroxide into the water, mixing it with the glass rods in such a way that it dissolves completely (Warning: strongly exothermic reaction, mix always in the same direction to avoid provoking burning splashes);
5. Once the hydroxide has completely dissolved, place the beaker in a water bath in the container filled with cold water, then immerse the thermometer in the solution and monitor the temperature;
6. In the process, place the beaker with the olive oil on the plate and warm over low heat by monitoring that the temperature is around 45, if it is necessary, remove the becher from the heating plate.
7. Once both becaker have reached a temperature of 45 degrees remove the thermometers and carefully insert the solution of hydroxide sodium in the beaker containing the olive oil,

 

 

 

Reaction mechanism:

• Hydroxide anion binds to the carbonyl group of the ester, producing orthoester;
• Expulsion of the alkoxide to generate carboxylic acid.
• Alkoxide ion is a strong base, consequently the proton is transferred from the carboxylic acid to the alkoxide, creating an alcool.