A LevelChemistryCIERevision Notes21. Organic Synthesis21.1 Organic SynthesisSynthetic Routes

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Synthetic Routes (CIE A Level Chemistry)

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Worked example

Analysis of Synthetic Routes

The synthesis of compound X takes place in 2 steps:

OHCCH2CHO rightwards arrow with step space 1 on top intermediate rightwards arrow with step space 2 on top HO2CCH(OH)CH2CH(OH)CO2H
        compound X

Which reagents could be used for this synthesis?

Answer:

  • The first step involves a nucleophilic addition of CN- using NaCN as catalyst and heat to form a hydroxynitrile
  • In the second step, the nitrile is refluxed with dilute aqueous sulfuric acid causing hydrolysis of the nitrile forming a carboxylic acid and ammonium salt

Organic Synthesis Answer Worked Example - Two-step synthesis, downloadable AS & A Level Chemistry revision notes

Worked example

The synthesis of hexanoic acid takes place in 2 steps

1-chloropentane rightwards arrow with reagent space straight X on top compound Z rightwards arrow with reagent space straight Y on top hexanoic acid

Which reagents could be used for this synthesis?

Answer:

  • Halogenoalkanes can undergo nucleophilic substitution with ethanolic KCN in which the CN- ion acts as a nucleophile and replaces the chlorine atom in 1-chloropentane to form a nitrile.
  • The treatment of nitriles with concentrated hydrochloric acid will produce a carboxylic acid and an ammonium salt.
  • In this case, hexanoic acid and ammonium chloride will be formed.

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    Philippa

    Author: Philippa

    Philippa has worked as a GCSE and A level chemistry teacher and tutor for over thirteen years. She studied chemistry and sport science at Loughborough University graduating in 2007 having also completed her PGCE in science. Throughout her time as a teacher she was incharge of a boarding house for five years and coached many teams in a variety of sports. When not producing resources with the chemistry team, Philippa enjoys being active outside with her young family and is a very keen gardener.