Question

(a) Name the reaction which is usually used in the conversion of vegetable oils to fats. Explain the reaction involved in detail. Write a chemical equation to illustrate your answer.
(b) What is saponification? Write the chemical equation of the reaction involved in this process. Name all the substances which take part in this process and also those which are formed.
(c) Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents like ethanol also?

Answer 1

(a) Catalytic hydrogenation is usually used in the conversion of vegetable oils to fats.
Hydrogenation of oils: Vegetable oils are unsaturated fats having double bonds between some of their carbon atoms and can undergo addition reactions. When a vegetable oil (like groundnut oil) is heated with hydrogen in the presence of finely divided nickel as a catalyst, then a saturated fat called vegetable ghee (for vanaspati ghee) is formed. This reaction is called hydrogenation of oils and it can be represented as shown in the figure.

(b) The process of making soap by the hydrolysis of fats and oils with alkalis is called saponification.

$\underset{Anester}{FatorOil}+\underset{\left(Analkali\right)}{Sodiumhydroxide}\stackrel{Heat}{\to }\underset{\left(\text{Sodium salt of fatty acid}\right)}{Soap}+\underset{\left(Analcohol\right)}{Glycerol}$.

(c) Soaps are sodium or potassium salts of long-chain carboxylic acids. When soap is added to the water, the hydrophilic end (acid end) will align along the surface of the water and the hydrophobic tall (carbon chain) remains out of water. When soap is dissolved in water, it forms a colloidal suspension in water in which the soap molecules cluster together to form spherical aggregates called micelles. In a soap micelle, soap molecules are arranged radially with hydrocarbon ends directed towards the centre and ionic end-directed outwards.
No, micelle will not be formed in other solvents such as ethanol because hydrocarbon chains of soap molecules are soluble in organic solvents like ethanol.