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: Define a cyclic amide.
An amide has the $-CO-NH-$ link. When that link is built inside a closed ring, the molecule is a lactam, a cyclic amide.
Step 2: Check PAN.
Polyacrylonitrile carries nitrile side groups $-C\equiv N$, with no amide, reject.
Step 3: Check terylene.
Terylene is a polyester made from ethylene glycol and terephthalic acid, holding ester links $-CO-O-$, not amide, reject.
Step 4: Check teflon.
Teflon is $-[CF_2-CF_2]_n-$ with only carbon and fluorine and no nitrogen, so no amide at all, reject.
Step 5: Check epsilon caprolactam.
It is a seven membered ring carrying an internal $-CO-NH-$ link, exactly a cyclic amide, and is the monomer for Nylon-6.
Step 6: Conclude.
The cyclic amide is $\varepsilon$-caprolactam, option (C).
\[ \boxed{\varepsilon\text{-caprolactam (option C)}} \]