Question

Nylon-4 is made by the polymerisation of

• A. 2-pyrrolidine
• B. Dodecalactum
• C. Amino undecanoic acid
• D. None of the above

Hint:

Ring-opening polymerisation of lactams produces different nylons depending on the number of carbon atoms.

Answer 1

The Correct Option is A

Step 1: Understanding nylon nomenclature.
The number in nylon (e.g., Nylon-4) indicates the number of carbon atoms present in the monomer unit used for polymerisation.
Step 2: Identifying the correct monomer.
Nylon-4 is produced by ring-opening polymerisation of 2-pyrrolidone (commonly written as 2-pyrrolidine in some texts). It contains four carbon atoms in the repeating unit.
Step 3: Eliminating incorrect options.
Dodecalactum is used for Nylon-12, and amino undecanoic acid is used for Nylon-11.
Step 4: Conclusion.
Hence, Nylon-4 is made by the polymerisation of 2-pyrrolidine.

Answer 2

Nylon numbering directly tells us the carbon count of the monomer used, so checking each candidate monomer's carbon count against the name "Nylon-4" identifies the right one.

1. 2-pyrrolidine (2-pyrrolidone): This monomer is a five-membered ring lactam with four carbon atoms in its backbone besides the ring nitrogen; ring-opening polymerisation of this monomer is exactly what produces Nylon-4, matching the "4" in its name.
2. Dodecalactum: This is the twelve-carbon lactam monomer, and its polymer is named Nylon-12, not Nylon-4, so it is the wrong monomer for this question.
3. Amino undecanoic acid: This eleven-carbon amino acid monomer polymerises to Nylon-11, again a different member of the nylon family from the one asked about.
4. None of the above: This would only be correct if none of the listed monomers matched Nylon-4, but 2-pyrrolidine is precisely the recognised Nylon-4 monomer, so this option is not needed.

Since the monomer's carbon count must match the "4" in the polymer's name, and only 2-pyrrolidine does so, it is the correct choice.

Therefore, the correct answer is 2-pyrrolidine.