Aldehydes and Ketones Flashcards
Aldehydes and ketones contain what?
A carbonyl group
Where do aldehydes have their carbonyl group?
At the end of the carbon chain- their names end in -al.
Where do ketones have their carbonyl group?
In the middle of the carbon chain- their names end in -one, and often have a number to show which carbon the carbonyl group is on.
How are aldehydes and carboxylic acids made?
By oxidising primary alcohols.
What is often used to oxidise alcohols?
Acidified potassium dichromate (VI)
To get just the aldehyde…
you need to get it out of the oxidising solution as soon as it’s formed.
To produce the carboxylic acid…
the alcohol has to be vigorously oxidised- the alcohol is mixed with excess oxidising agent and heated under reflux.
How are ketones made?
By oxidising secondary alcohols.Refluxing a secondary alcohol with acidified dichromate (VI) will produce a ketone.
Using a reducing agent you can:
1) Reduce an aldehyde to a primary alcohol.2) Reduce a ketone to a secondary alcohol.You’d usually use NaBH4 dissolved in water with methanol as the reducing agent.
What is Brady’s reagent used for?
Tests for a carbonyl group.If present, bright orange precipitate forms.
What is Tollens’ reagent and what is it used for?
It is a colourless solution of silver nitrate dissolved in aqueous ammonia- when heated together in a test tube, the aldehyde is oxidised and Tollens’ reagent is reduced causing a silver mirror to form.Distinguish between an aldehyde and ketone.It uses the fact an aldehyde can be easily oxidised to a carboxylic acid, but a ketone can’t.
