Question

On complete hydrogenation, natural rubber produces
(A) ethylene-propylene copolymer
(B) vulcanised rubber
(C) polypropylene
(D) polybutylene

Answer 1

Hint: For this problem, we have to study the formation of the natural polymer and its formula which will then undergo hydrogenation in the presence of hydrogen and a catalyst. Then we will get the correct answer.

Complete step by step solution:
-In the given question we have to determine the correct product which is formed after the hydrogenation of the natural rubber.
-Hydrogenation is a chemical in which the addition of hydrogen takes place by the breaking of unsaturated bonds with the help of metal catalysts such as nickel.
-The process helps in converting the unsaturated hydrocarbon into saturated hydrogen.
-As we know that natural rubber is a polymer because it is by the polymerisation reaction of the monomer isoprene or 2-methyl - 1,3 butadiene.
-When so many molecules of isoprene make bonds with each other they yield cis - 1,4 polyisoprene.
- The balanced chemical reaction is shown below:

-When this natural rubber undergoes complete hydrogenation reaction, the double bond break and it yields copolymer of ethylene and propylene i.e.
$\text{Natural rubber }\xrightarrow{{{\text{H}}_{2}}/\text{Ni}}\text{ -C}{{\text{H}}_{2}}\text{ - CH (C}{{\text{H}}_{3}}\text{) - C}{{\text{H}}_{2}}\text{ - C}{{\text{H}}_{2}}\text{- }\to \text{ C}{{\text{H}}_{2}}\text{ = C}{{\text{H}}_{2}}\ \text{+ C}{{\text{H}}_{2}}\text{ = CH - C}{{\text{H}}_{3}}$
-Here, nickel, palladium, etc will act as a catalyst which will increase the rate of reaction.

Therefore, option A is the correct answer.

Note: Copolymer is the type of polymer which is made up by the polymerisation of different types of monomer. The process of hydrogenation is also known as reduction reaction because the reduction of molecules takes place by addition of hydrogen.