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A LevelChemistryCIERevision Notes7. Organic Chemistry (A Level Only)7.7 Polymerisation (A Level Only)7.7.3 Repeat Units & Monomers

Repeat Units & Monomers (CIE A Level Chemistry)

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Francesca

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Francesca

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Deducing the Repeat Unit of a Condensation Polymer

  • In condensation polymerisation the monomers either contain 2 of the same functional group or one single monomer has both functional groups needed for polymerisation
    • For example Diamine and dicarboxylic acid
    • Or an aminocarboxylic acid

  • When presented with 2 monomers there are steps to take in order to deduce the repeat unit of a condensation polymer

Examiner Tip

  • Remember: in condensation polymerisation, a small molecule is expelled as a result of the 2 monomers joining together.
  • When a dioic acid and diamine polymerise, a water molecule is expelled
    • OH from acid and H from the amine

  • When a dioyl acid and diamine are polymerised, a hydrochloric acid molecule is expelled
    • Cl from the dioyl acid and H from the amine

Identifying Monomers in Condensation Polymers

  • When a section of polymer is presented, the monomers can be identified by considering the small molecules expelled from the monomers
  • If a water molecule is expelled, the -OH must have been from an acid group
  • The hydrogen atom may be from an amine group of a monomer.
  • If the molecule was hydrochloric acid (HCl), a dioyl chloride monomer may have been used

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    Francesca

    Author: Francesca

    Expertise: Head of Science

    Fran studied for a BSc in Chemistry with Forensic Science, and since graduating taught A level Chemistry in the UK for over 11 years. She studied for an MBA in Senior Leadership, and has held a number of roles during her time in Education, including Head of Chemistry, Head of Science and most recently as an Assistant Headteacher. In this role, she used her passion for education to drive improvement and success for staff and students across a number of subjects in addition to Science, supporting them to achieve their full potential. Fran has co-written Science textbooks, delivered CPD for teachers, and worked as an examiner for a number of UK exam boards.