Multi-Step Synthetic Routes
- A large number of organic products are made from a few starting compounds using appropriate reagents and conditions
- Knowing how organic functional groups are related to each other is key to the synthesis of a given molecule
- The main functional groups you need to know are
- Alkanes
- Alkenes
- Haloalkanes
- Nitriles
- Amines
- Alcohols
- Carbonyls (aldehydes & ketones)
- Hydroxynitriles
- Carboxylic acids
- Esters
- Acyl chlorides
- Primary and secondary amides
Examiner Tip
You also need to be able to identify the functional groups of these chemicals in structures that are given to you
Aliphatic Reaction Pathways
- The key interconversions between functional groups are summarised here:
Aliphatic Reactions Table
Aromatic Reaction Pathways
- The key aromatic reactions are summarised here:
Aromatic Reactions Table
Designing a Reaction Pathway
- The given molecule is usually called the target molecule and chemists try to design a synthesis as efficiently as possible
- Designing a reaction pathway starts by drawing the structures of the target molecule and the starting molecule
- Determine if they have the same number of carbon atoms
- If you need to lengthen the carbon chain you will need to put on a nitrile group by nucleophilic substitution
- Work out all the compounds that can be made from the starting molecule and all the molecules that can be made into the target molecule
- Match the groups they have in common and work out the reagents and conditions needed
Worked example
Suggest how the following synthesis could be carried out:
Ethene to 1-aminopropane
Answer
Examiner Tip
Sound knowledge of all of the different reactions is beneficial as the A-level course simply states that you should be able to design a multistage synthesis
Past papers generally go to four steps in a multistep reaction although there is no clear limit stated
