Which of the following are the monomers for the polymer dacron?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Ethylene glycol and Terephthalic acid
Dacron (terylene) is a polyester made by condensation polymerisation of ethylene glycol (ethane-1,2-diol) and terephthalic acid (benzene-1,4-dicarboxylic acid). Each ester link forms with loss of a water molecule:
\( \ce{n HOCH2CH2OH + n HOOC-C6H4-COOH -> [-OCH2CH2O-CO-C6H4-CO-]_n + 2n H2O} \)
It is used in crease-resistant fabrics and in blends with cotton and wool.
Why the other options are incorrect
Option (1) Hexamethylenediamine and Terephthalic acid — Incorrect. A diamine with a diacid gives a polyamide, not the polyester dacron.
Option (2) Caprolactam and Adipic acid — Incorrect. Caprolactam alone gives nylon 6; it is not combined with adipic acid in any common polymer.
Option (3) Ethane 1, 2-diamine and Adipic acid — Incorrect. A diamine with adipic acid gives a polyamide; nylon 6,6 is made from hexamethylenediamine and adipic acid.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Condensation Polymerisation or Step Growth Polymerisation
