Aldehydes And Ketones Flashcards
What type of group do aldehydes and ketones contain?
A carbonyl group
What is the difference between the carbonyl groups in aldehydes and ketones
• Carbonyl group is located in different positions
• Aldehydes: carbonyl group is at the end of the carbon chain- al
• Ketones: Carbonyl group is in the middle of the carbon chain- one
What do aldehydes produce when oxidised?
Carboxylic acids
Why can’t ketones be oxidised
They do not have a hydrogen attached to their carbonyl
What happens to the other compound when an aldehyde is oxidised
The other compound is reduced
Give the two oxidising agents to test for aldehydes and ketones and the product of the reaction
- Tollens reagent: colourless solution of silver nitrate dissolved in aqueous ammonia
- Tollens reagent is heated in a test tube with an aldehyde, Ag+ ions are reduced to Ag atoms and a silver mirror forms
- Ketones can’t be oxidised so there’s no colour change
- Fehling’s solution/benedict’s solution: blue solution of copper (II) ions dissolved in sodium hydroxide
- Heated with an aldehyde , the copper (II) ions are reduced to a brick-red precipitate of copper (I) oxide
- With ketones, no precipitate is formed
What product is formed when aldehydes are reduced?
Alcohols
What product is formed when secondary alcohols are oxidised
They form ketones
What reducing agent is used to reduce aldehydes to alcohols
NaBH4 (sodium tetrahydridoborate (III) or sodium borohydride
What type of reaction is the reduction of aldehydes to produce alcohols
• Nucleophilic addition reactions
• H- ions acts as a nucleophile and adds on to the s+ carbon atom
Give the diagram for the reduction of aldehydes to form primary alcohols and ketones to secondary alcohols
Check physical flashcards for answers
Give a detailed diagram of how aldehydes are reduced
Check physical flashcards for answers
Where do the H- ions and H+ ions come from?
• H-: from the reducing agent
• H+: from water
How does potassium cyanide react with carbonyls?
By Nucleophilic addition reactions
What is the product of the reaction of potassium cyanide and carbonyls
Hydroxynitriles, molecules with a CN and an OH group