10. Aldehydes and ketones Flashcards
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
