Seneca
Sign up

Examples of Synthetic Routes (A2 Only)

Chemistry: AQA A Level, topic 6.8.2

Methyl Benzene → Aromatic Ester

How can we produce an aromatic ester from a methyl benzene?

Overall reaction

Overall reaction

  • We must consider the overall reaction as shown above.
  • An ester group must be added to the side chain of the benzene molecule.
First step

First step

  • First, we substitute a hydrogen for a chlorine atom.
  • This introduces a C-Cl bond.
  • The conditions are:
  • Cl2
  • UV light.
Second step

Second step

  • Next we substitute the Cl atom for an OH group.
  • The reaction is carried out under reflux.
  • This is a substitution reaction.
  • The product is an alcohol.
Third step

Third step

  • Lastly, we react the alcohol group with a carboxylic acid to form an ester group.
  • The conditions are:
  • H+ catalyst.
  • Under reflux.

Benzene → Aromatic Amide

How can we obtain the aromatic amide starting from a benzene molecule?

Overall reaction

Overall reaction

  • First, we consider the overall reaction as shown above.
First step

First step

  • In the first step, we nitrate the benzene ring.
  • This introduces a -NO2 group, as shown above.
  • The conditions for this are:
  • HNO3.
  • H2SO4 catalyst.
  • 50oC.
Second step

Second step

  • Next we reduce the nitrated benzene using:
  • Tin.
  • HCl.
  • This forms the protonated product shown above.
Third step

Third step

  • To neutralise the protonated amine, we must add base.
  • We obtain the aminobenzene, as shown.
Fourth step

Fourth step

  • Lastly, we carry out the condensation reaction to create the amide bond using an acyl chloride.
  • The conditions for this are:
  • Use acid catalyst.
  • Under reflux.

Ethene → Propylamine

How can we form a propylamine molecule from ethene?

Overall reaction

Overall reaction

  • We consider the overall reaction, shown above.
First step

First step

  • The alkene undergoes an addition reaction to gain a Cl and an H atom across the double bond.
  • Requires an HCl reagent.
Second step

Second step

  • Next, we substitute the Cl atom for a CN group.
  • The conditions are:
  • Ethanol/water.
  • Under reflux.
Third step

Third step

  • Lastly, we reduce the cyanide group to form an amine group.
  • This requires a reducing agent.
  • We use LiAlH4

Test yourself on Examples of Synthetic Routes (A2 Only)

  • What are the conditions for the second step of the synthesis (where we replace a C-Cl bond for a C-OH bond)?

  • Carboxylic acid and an acid catalyst react under reflux with which of the following to form an ester group?

  • Which of the following is NOT involved in replacing the NO2 group for an NH2 group?

  • There is only one reagent for the first step of this reaction (an addition to an alkene). What is the reagent?

  • Which step of the reaction ethene → propylamine is carried out under reflux?

Practise this topic for free