2001 AIPMT PolymersStructures of Common Polymers Medium Question 33 of 34 in Polymers

Which of the following is not correctly matched

A Neoprene – $[-CH_2-C(Cl)=CH-CH_2-]_n$
B Nylon-66 – $[-NH-(CH_2)_6-NH-CO-(CH_2)_4-CO-O-]_n$
C Terylene – $[-OCH_2-CH_2-CO-C_6H_4-CO-]_n$
D PMMA – $[-CH_2-C(CH_3)(COOCH_3)-]_n$

The answer is C.

Solution

Neoprene is polychloroprene, $[-CH_2-C(Cl)=CH-CH_2-]_n$; correctly matched.
PMMA (polymethyl methacrylate) is $[-CH_2-C(CH_3)(COOCH_3)-]_n$; correctly matched.
Terylene (Dacron) is a polyester of ethylene glycol and terephthalic acid. Its repeat unit is $[-O-CH_2-CH_2-O-CO-C_6H_4-CO-]_n$, with an ester oxygen between each $CH_2$ and C=O.
The structure given for terylene, $-OCH_2-CH_2-CO-C_6H_4-CO-$, has no oxygen between $CH_2$ and C=O, so it is not the correct ester structure.
(The Nylon-66 unit is written with an extra O, but the key treats it as matched; nylon-66 is $[-NH-(CH_2)_6-NH-CO-(CH_2)_4-CO-]_n$.)
So, as per the answer key, terylene is not correctly matched.

Concept Repeat unit of Terylene

Polymers in past papers

34 questions from this chapter have appeared across 23 exam years.