Question

(a) Name the reaction which is usually used in the conversion of vegetables 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 the reaction usually used to convert vegetable oils to fats. Hydrogenation is a process in which hydrogen molecules are added to an unsaturated hydrocarbon in the presence of a catalyst to obtain a saturated hydrocarbon. In this process, the double bonds are removed from the unsaturated compounds (oils).
For example: When hydrogen is added to vegetable oils (unsaturated), a saturated product called ghee (semi-solid) is obtained.

The chemical equation of this hydrogenation reaction in the presence of catalyst nickel is shown below:

${\mathrm{R}}_2\mathrm{C}={\mathrm{CR}}_2+{\mathrm{H}}_2\stackrel{}{\to {\mathrm{R}}_2\mathrm{HC}-{\mathrm{CHR}}_2}$

(b) Saponification is a process of preparing soap by the hydrolysis of fats or oils with alkalis.
When animal fat or vegetable oil (ester) is heated with concentrated sodium hydroxide solution, soap and glycerol (alcohol) are formed.

Equation: Fat or oil (Ester) + Sodium Hydroxide → Soap + Glycerol (an alcohol)

The chemical equation is as follows:


(c) Micelles are formed when soap is added to water. This is because the hydrocarbon chains of a soap molecule are hydrophobic and insoluble in water, but the ionic ends are hydrophilic and soluble in water. Micelles are an aggregate of soap molecules that arrange themselves in a spherical shape in the soap solution.
Micelles will not form in a solvent like ethanol, as the hydrocarbon chain of soap molecules is hydrophobic; hence, not be soluble in organic solvent like ethanol.