Describe the addition reaction of carbon compounds with its application. State the functions of catalyst in this reaction. How this reaction is different from a substitution reaction? Explain with example.

Explanation

The addition of hydrogen to an unsaturated molecule to make it saturated is known as hydrogenation or addition reaction.
Example: Ethene undergoes addition reaction to form ethane.
`underset("(Unsaturated)")underset("Ethane")(CH_2 = CH_2 + H_2) underset(N i)overset(200^@C)(rarr) underset("(Saturated"))underset("Ethane")(CH_3 - CH_3)`
This reaction is applied to convert unsaturated vegetable oil into saturated ghee.
`underset(("unsaturated"))("Vegetable oil") underset("200^@C)overset(H_2//N i)(rarr) underset(("Saturated"))("Ghee") " [Hydrogenation"]`
The rate of reaction is increased in the presence of catalyst Ni or Pt. This is addition reaction. In substitution reaction, reagent substitutes on atoms or a group of atoms from the reactant instead of addition.
Eg. `CH_4 + Cl_2 underset("Sunlight")(rarr) underset("Chloromethane")(CH_3Cl) + HCl`