MolSynapsequestion bank
MolSynapse / Question bank / Polymers / Functional groups and hydrolysis of drawn polymers
JEE Advanced levelSingle correct optionDifficulty 3 of 3pl275

A short fragment of a polyester chain (one repeat unit with a free carboxylic acid end, end groups shown) is drawn. It is heated with an excess of aqueous sodium hydroxide until all ester and acid groups have reacted completely. Which pair (or set) of species, shown as molecules among the structures, is obtained?

  1. AStructure A
  2. BStructure B
  3. CStructure C
  4. DStructure D

Answer: C

The fragment is a piece of PET. Alkaline hydrolysis cleaves the ester into ethylene glycol and the carboxylate; with excess NaOH both carboxyl groups are present as the disodium salt, disodium terephthalate. Free terephthalic acid would form only after acidification, the ortho salt corresponds to a different ring, and the monosodium salt would leave one acidic group unreacted.
Practice Polymers More on Functional groups and hydrolysis of drawn polymers
Previous question

More questions on Functional groups and hydrolysis of drawn polymers