What other name are the aldehydes known by?
The Alkanals
What other name are the ketones known by?
Alkanones
What is the general formula of aldehydes and ketones?
Cn H2n O
What functional group do aldehydes and ketones share?
The carbonyl group
Where is the carbonyl group found in aldehydes?
Always on the first C atom.
Where is the carbonyl group found in ketones?
On an “inside” C atom between 2 alkyl groups.
(alkyl groups represented by R here)
How are aldehydes formed?
- oxidation of a primary alkanol
- reduction of a carboxylic acid
How are ketones formed?
oxidation of a secondary alkanol
How can aldehydes be distinguished from ketones?
Aldehydes only will give a positive test with
- tollen’s reagent
- fehling’s solution
What change is observed with Tollen’s reagent?
A silver mirror forms
What change is observed with Fehling’s solution?
Blue to orange/red
What colour change is observed with acidified potassium dichromate solution?
Orange to green
Why must potassium dichromate solution be acidified?
As a source of H+ (aq) ions
What reactions do aldehydes undergo?
- oxidation to carboxylic acids
- reduction to primary alkanols
What reactions do ketones undergo?
reduction to secondary alkanols