Aldehydes and ketones Flashcards
a2 chem
What functional group do aldehydes and ketones have and what is the difference between them?
They have a carbonyl functional group c=o.
The difference between the aldehyde and ketone is the position of the carbonyl (c=o) group.
Aldehydes (‘AL’) have the carbonyl group on the end of the carbon.
Ketones have the carbonyl group in the middle (‘ONE’)
Describe oxidation of aldehydes
Aldehydes are oxidised to carboxylic acids using an oxidising agent.
Describe oxidation of Ketones
They do not get oxidised.
How do you distinguish for aldehydes and ketones?
Tollens reagent:
silver nitrate + few drops of NAOH and then add dilute ammonia.
Add aldehyde or ketone and place in warm water bath. If aldehyde is present silver mirror will form.
Fehling’s solution:
Blue solution add to solution place in warm water bath . If aldehyde is present then red precipitate is formed.
What is fehlings solution and tollens reagent?
Oxidising agents
How is aldehydes reduced?
Condition:
using a reducing agent- NaBH4 dissolved in methanol and water. (H)
Produces:
primary alcohols
How is ketones reduced?
Condition:
using a reducing agent- NaBH4 dissolved in methanol and water. (H)
Produces:
secondary alcohols.
What mechanism do aldehydes and ketones under go?
Nucleophillic addition
How are hydroxynitriles produced from ketones and aldehydes?
They are produced from nucleophilic addition , where a nucleophile (CN- Ion) attacks the carbonyl group and adds on to make hydroxynitrile.
How are CN- ions produced to be used in nucleophilic addition reaction?
Potassium cyanide is used to produce CN- ions when dissolved in acidic solution.
Why is potassium cyanide used rather than hydrogen cyanide?
HCN is hard to store as a gas and reacts to produce dangerous byproducts it is toxic.
What is dangerous about using potassium cyanide and what safety measures can we use?
It is an irritant and is very dangerous of ingested or inhaled.
When potassium cyanide reacts with moisture it can form the toxic gas, hydrogen cyanide.
Safety Measures:
- wear safety goggles
- wear gloves
- Wear a lab coat
