Ethylene glycol and terephthalic acid are the monomeric unit for the formation of:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Dacron
Dacron (terylene) is a polyester made by condensation (step-growth) polymerisation of ethylene glycol (ethane-1,2-diol) and terephthalic acid (benzene-1,4-dicarboxylic acid). Each ester link forms with the loss of a water molecule:
\( \displaystyle \ce{n HOCH2CH2OH + n HOOC-C6H4-COOH -> [-OCH2CH2O-CO-C6H4-CO-]_n + 2n H2O} \)
It is used in crease-resistant fabrics and in safety helmets.
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 – “This type of polymerisation generally involves a repetitive condensation reaction between two bi-functional monomers. These polycondensation reactions may result in the loss of some simple molecules as water, alcohol, etc., and lead to the formation of high molecular mass condensation polymers. In these reactions, the product of each step is again a bi-functional species and the sequence of condensation goes on. Since, each step produces a distinct functionalised species and is independent of each other, this process is also called as step growth polymerisation. The formation of terylene or dacron by the interaction of ethylene glycol and terephthalic acid is an example of this type of polymerisation.”