Question

The monomer of Nylon-6 is:
(A) Cyclohexane
(B) Caprolactam
(C) Ethylene glycol
(D) Amino acid

Answer 1

Hint: Nylon-6 or polycaprolactam is a semicrystalline polyamide. While comparing with other nylons, nylon-6 is not a condensation polymer; instead, it is formed by ring opening polymerisation. Also, this peculiarity makes it a special case in the comparison between condensation and addition polymers.

Complete step by step solution:
Nylon-6 or polycaprolactam ( $ {({C_6}{H_{11}}NO)_n} $ ) is usually produced by ring opening chain growth polymerisation of caprolactam in presence of water vapour and an acid catalyst at the melt. It is then drawn into the form of fibres by melting nylon-6 at $ 250 - 260^\circ C $ after the removal of water and acid.
In order to change the reactivity and chemical properties nylon-6 is modified using comonomers or stabilizers during polymerisation thereby introducing a new chain end or functional group.
In this process of manufacturing nylon-6 caprolactam is used as the monomer. It is an organic compound having the chemical formula of $ {C_6}{H_{11}}NO $ . It is a cyclic amide called lactam formed from caproic acid. It is a colourless compound which is produced by the cyclization of aminocaproic acid, the product of the hydrolysis of caprolactam.
Since caprolactam is the monomer of Nylon-6,
$ \therefore $ Option B is the answer.

Additional Information:
 $ 90\% $ of the caprolactam produced is used to make filaments and fibres and the rest $ 10\% $ is used in the manufacture of plastics and a small amount is used as a chemical intermediate. As caprolactam is having high commercial significance there are many methods developed for the production of caprolactam. It was estimated that about $ 90\% $ of the caprolactam is produced from cyclohexanone which is initially converted to its oxime. The oxime thus produced is treated with an acid which induces Beckmann reagent to produce caprolactam.

Note:
Most of the caprolactam produced is used in the manufacture of nylon-6 which is widely used in the manufacture of fibres and plastics. Caprolactam is also used in the manufacture of many types of pharmaceutical drugs which include pentylenetetrazol, meptazinol, laurocapram.