CIE AS Chemistry (9701) exams from 2022

Revision Notes

3.9.3 Synthetic Routes

Analysis of Synthetic Routes

  • Students should be able to critically analyse given synthetic routes and determine whether appropriate reagents and reaction conditions are used
  • Students should also be able to predict possible by-product of a synthetic reaction

Worked Example: Two-step synthesis

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

Answer

The correct answer is  D

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: Synthesis of hexanoic acid

 

Organic Synthesis Worked Example - Synthesis of hexanoic acid, downloadable AS & A Level Chemistry revision notes

 

Answer

The correct answer is C

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.

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
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