Aldehydes and ketones

• The carbonyl group (C=O) is the functional group in carbonyl molecules.
• A carbonyl compound is any molecule that contains a carbonyl group
• In an aldehyde, the carbonyl group is bonded to either a carbon and a hydrogen or a hydrogen and a hydrogen
• The structural formula of an aldehyde is RCHO
• The suffix of an aldehyde is -anal
• The carbonyl group in a ketone is bonded to two carbons
• The structural formula for a ketone is RCOR'
• The suffix for a ketone is -anone
• Carbonyl compounds all experience both Van der Waals forces and dipole-dipole forces
• Aldehydes are useful starting materials in the synthesis of a wide variety of organic compounds
• Why are carbonyl compounds more soluble than other polar molecules?

  Their O can hydrogen bond to water
• What is a carbonyl group?

  C=O
• Tollens' reagent is formed by mixing aqueous ammonia and silver nitrate, to form the active complex of silver (I) ions
• When Tollens' is warmed with an aldehyde, silver atoms coat the test tube and produce an effect called the silver mirror
• In the Tollens' test, a silver mirror is produced when the silver (I) ions are reduced to silver atoms as the aldehyde is oxidised to a carboxylic acid
• Tollens' equations:

  Ag+ + e- -> Ag

  RCHO + [O] -> RCOOH
• Fehling's solution contains blue copper (II) ions as a copper complex.
• Copper (II) ions act as a weak oxidising agent and will oxidise an aldehyde to a carboxylic acid, whilst being reduced to copper (I) ions in the form of the brick red precipitate copper oxide
• Alcohols can be oxidised to aldehydes or ketones
• Aldehydes can be oxidised. Ketones cannot be oxidised
• Aldehydes oxidise to carboxylic acid
• Sodium borohydride or sodium tetrahydridoborate is a commonly used reducing agent
• We dissociate sodium borohydride in water to form Na+ ions and BH4- ions
• BH4- is a form of hydride (H-) ions
• Lithium aluminium hydride (LiAlH4) is also a good source of hydride ions
• The hydride ion is attracted to the partially positive carbon from the polar carbonyl group
• The reduction of ketones produces secondary alcohols. If the ketone is asymetrical, a chiral molecule is formed
• optical isomers are produced when asymmetrical ketones are reduced
• the reduction of asymmetrical ketones produces a racemic mixture since each enantiomer has an equal probability of forming
• Carbonyl bonds form a trigonal planar arrangement, so when reacting with a reducing agent, a bond between the carbon and hydride ion can form from either side