Topic B6: Carbonyls
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What reactants are required for oxidation of aldehydes?
-potassium dichromate (VI) -dilute sulfuric acid
What is the product of oxidation of aldehydes?
carboxylic acid
Can ketone’s be oxidised?
no
What is the colour change of aldehydes oxidation?
orange —> green
Why do aldehydes and ketones react with nucleophiles?
as the C=O bond is polar, hence the nucleophile is attracted to and attacks the slightly positive carbon atom
What is the name for the reaction of aldehydes/ ketones with nucleophiles?
nucleophilic addition
Aldehyde + NaBH4 —>
primary alcohol
Conditions of reduction of aldehydes to primary alcohol
-reducing agent (e.g. NaBH4) -aqueous solution -warmed/ heated
Ketones + NaBH4 —>
secondary alcohol
What is the reaction called when converting ketone to a secondary alcohol?
reduction
How is an hydroxynitrile formed?
aldehyde/ ketone + HCN
What test is used to detect the presence of a carbonyl (C=O) functional group?
2,4-DNPH (Brady’s Reagent)
What is produced when a carbonyl group is reacted with 2,4-DNPH (Brady’s reagent)?
yellow or orange precipitate
How do you distinguish between aldehydes and ketones in a chemical test?
Tollens’ Reagent -solution of silver nitrate -aqueous ammonia
What is the result of an aldehyde + Tollens’ reagent?
silver mirror is produced
What happens to the aldehyde in its reaction with Tollens’ reagent?
-aldehyde is oxidised (as silver (I) ions are reduced) -aldehyde —> carboxylic acid