Question

Which among following is an example of cyclic amide?

• A. PAN
• B. Terylene
• C. $\varepsilon$-caprolactam
• D. Teflon

Hint:

In organic chemistry, remember the special terminology for cyclic functional groups: a cyclic ester is called a lactone, whereas a cyclic amide is always called a lactam (like $\varepsilon$-caprolactam)!

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The problem requires us to evaluate the given chemical choices and identify which compound contains a cyclic amide functional group.

Step 2: Key Formula or Approach:
An amide group is defined by a carbonyl carbon bound to a nitrogen atom ($\mathrm{-CO-NH-}$). When this amide group is incorporated directly into a closed ring system, the molecule is classified as a

lactam (cyclic amide).

Step 3: Detailed Explanation:
Let's review the structural classifications of the choices:

• PAN (Polyacrylonitrile): Formed via addition polymerization of acrylonitrile; it features side-chain nitrile groups ($\mathrm{-C\equiv N}$), not amides.

• Terylene: A polyester compound derived from ethylene glycol and terephthalic acid, containing ester linkages ($\mathrm{-CO-O-}$).

• $\varepsilon$-caprolactam: A seven-membered cyclic ring structure containing an internal $\mathrm{-CO-NH-}$ bond. This configuration precisely satisfies the chemical definition of a cyclic amide (lactam). It serves as the primary monomer starting material for preparing Nylon-6 via ring-opening polymerization.

• Teflon: Polytetrafluoroethylene ($\mathrm{-[CF_2-CF_2]_n-}$), a fluoropolymer entirely lacking nitrogen or oxygen atoms.

Step 4: Final Answer:
The example of a cyclic amide is $\varepsilon$-caprolactam, matching option (C).