Two-Stage Organic Synthetic Routes
- It is possible to make a large number of organic products from a few starting compounds and the necessary 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
- Alcohols
- Carbonyls (aldehydes & ketones)
- Carboxylic acids
Aliphatic Reaction Pathways
- The key functional groups and their interconversions are summarised here:
The main reaction pathways at AS level
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:
Chloroethane to ethanoic acid
Answer
Exam Tip
At AS level, you will only be required to design a synthesis with two steps, i.e. reactant → intermediate → product
However, sound knowledge of all of the different reactions will be beneficial in the long run - especially as the A-level course simply states that you should be able to design a multistage synthesis
