26.1 Carbonyl Compounds
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What is the carbonyl functional group?
C=O
Carbonyl group in aldehydes
Carbonyl group found at the end of the carbon chain CHO
Simplest aldehyde
Methanal
Common name for methanal
Formaldehyde
Carbonyl group in ketones
Carbonyl functional group is joined to 2 Carbon atoms CO
Simplest ketone
Propanone
Common name for propanone
Acetone
Suffixes for aldehyde
-al
Suffixes for ketone
-one
Oxidation of aldehydes
Aldehydes can be oxidised to form carboxylic acids
Conditions for oxidation of aldehydes
Reflux with Potassium Dichromate and dilute sulfuric acid
Can ketones be oxidised?
No, they cannot
What does the reactivity of aldehydes and ketones depend on?
Nature of the Carbon-Oxygen double bond Made of sigma bond and pi bond
Why is the double bond in alkenes different to the C=O bond?
C=C bond is non polar C=O bond is polar
Why is the C=O bond polar?
Oxygen is more electronegative than Carbon Electron density in the double bond is closer to the Oxygen atom than the Carbon Carbon becomes δ+ and Oxygen becomes δ-
Reactions of aldehydes and ketones
Undergo nucleophilic addition
Reducing agent for reduction of ketones and aldehydes
Sodium Tetrahydridoborate (III) NaBH4
Reduction of aldehydes
Reduced to primary alcohols
Reduction of ketones
Reduced to secondary alcohols
Hydrogen cyanide
Colourless extremely poisonous liquid Boils slightly above room temperature Cannot be used safely in laboratory
Why is NaCN used instead of HCN?
It’s formed in situ Exists as a solid, so it is safer to use
Why is the reaction with HCN useful?
Allows the carbon chain to be extended
Compound formed when carbonyl compounds react with HCN
Hydroxynitrile -OH and CN (triple bond)