20.2.1 Synthesis

• 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
  • Halogenoalkanes
  • Alcohols
  • Carbonyls (aldehydes & ketones)
  • Carboxylic acids and derivatives
  • Arenes

Aliphatic Reaction Pathways

• The key functional groups and their interconversions are summarised here:

The main reaction pathways in aliphatic chemistry

Aliphatic Chemistry Reactions Table

Aromatic Reaction Pathways

• The key aromatic reaction for this course is:

The nitration and reduction reactions to form phenylamine from benzene

Aromatic Nitration and Reduction Reactions Table

Choosing A Reaction Pathway

• Chemists will often have several choices of reaching a target molecule and those choices need to take into the principles of green chemistry

The twelve principles of green chemistry

• By choosing a pathway that has fewer steps, you can prevent waste and reduce energy demands which is better for the environment
  • This also reduces production costs

• By analysing the atom economy of each step, you can select reactions that give a higher atom economy
• Choosing alternative safer solvents also follows the principles of green chemistry

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
• 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

Answer