(A) The monomer A on ozonolysis yields two molecules of HCHO and a molecule of CH$$_3$$COCHO. During ozonolysis, the double or triple bonds in the molecule are replaced by carbonyl groups.

Therefore, if we remove the oxygen atoms from 2 molecules of HCHO and a molecule of CH$$_3$$COCHO and replaced them with double bond, we can deduce the structure of monomer A.

IIT-JEE 2005 Mains Chemistry - Polymers Question 3 English Explanation 1

The structure of monomer A we got is the structure of isoprene. Therefore, monomer A is isoprene.

(B) The isoprene is a monomer for natural rubber.

IIT-JEE 2005 Mains Chemistry - Polymers Question 3 English Explanation 2

To write the “all $$cis$$” form of the polymer of monomer A that is isoprene, we need to write the structure of polymer such that the identical groups present across double bonds should lie in the same plane.

The “all $$cis$$” for of the polymer is shown below.

IIT-JEE 2005 Mains Chemistry - Polymers Question 3 English Explanation 3

Final Answer

IIT-JEE 2005 Mains Chemistry - Polymers Question 3 English Explanation 4

Hints:

The ozonolysis eliminates the double or triple bond from the molecule and replace it with carbonyl groups. The removal of oxygen atoms and replacing it with double bonds will give the structure of monomer A.

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