Aldehydes and Ketones
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If C=O is on the end of the chain it is…?
An aldehyde
If C=O is in the middle of the chain it is..?
A ketone
Name ending for aldehydes?
-al.
Name ending for ketones?
-one.
What forces are present in aldehydes and ketones?
Van der waals. Permanent dipole forces.
Can aldehydes and ketones form hydrogen bonds?
Not with themselves.
Why are smaller carbonyls soluble in water?
They can form hydrogen bonds with water.
Describe the polar bond in C=O.
It is polarised because O is more electronegative than C. The positive carbon atom attracts nucleophiles.
Why don’t aldehydes and ketones undergo addition reactions easily?
The C=O bond is stronger than the C=C bond which is why electrophiles are attracted to the C=C.
What oxidising agent oxidises alcohols and aldehydes?
Potassium dichromate
What can a primary alcohol be oxidised into?
Aldehyde then aldehydes can be oxidised into carboxylic acids.
What can a secondary alcohol be oxidised into?
A ketone only since ketones can’t be oxidised.
What can a tertiary alcohol be oxidised into?
Nothing
What reagents are needed for the oxidation of aldehydes into carboxylic acids? What condition is needed?
Dilute sulfuric acid and potassium dichromate solution. Heat under reflux.
What is seen in the oxidation of aldehydes into carboxylic acids?
Turns from orange to green.
What can be used to test for aldehydes?
Tollens’ Reagent Fehling’s Solution
What condition is needed for Tollens’ Reagent? What happens in the reaction? What can you observe?
1) Heat gently 2) Aldehydes are oxidised into a carboxylic acid. 3) Silver mirror forms.
What condition is needed for Fehling’s solution? What happens in the reaction? What can you observe?
1) Heat gently 2) Aldehydes are oxidised into a carboxylic acid. 3) Turns from blue to brick red precipitate.
Which reducing agents reduce carbonyls into alcohols?
LiAlH4 NaBH4
What is NaBH4?
Sodium Tetrahydridoborate.
What is LiAlH4?
Lithium Tetrahydridoaluminate.
What conditions are needed for the reduction of carbonyls?
Room temperature and pressure
What are aldehydes reduced into?
Primary alcohols
What are ketones reduced into?
Secondary alcohols