OCR A2 Chemistry: Aldehydes and Ketones

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  • Created by: LucySPG
  • Created on: 15-09-13 15:54
What functional group do aldehydes and ketones contain?
Carbonyl group
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What is it about the aldehyde that gives them different properties to ketones?
The presence of a hydrogen atom attached to the carbonyl group
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How are aldehydes and ketones prepared?
By oxidation
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What type of alcohol is an aldehyde?
Primary alchol
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What type of alcohol is a ketone?
Secondary alcohol
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What is the oxidising agent used to oxidise aldehydes and ketones?
Acidified potassium dichromate
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How is acidified potassium dichromate solution made?
Dissolving potassium dichromate in dilute sulphuric acid
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Why is an aldehyde distilled off as soon as it is formed?
To prevent further oxidation of an aldehyde to a carboxylic acid
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How can you distinguish between an aldehyde and a ketone?
By reacting them with Fehlings solution. The aldehyde is oxidised to a carboxylic acid and the blue Cu2+ ions are reduced to Cu+ in copper oxide. This forms an orange/brown precipitate.
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What happens to the colour of the acidified potassium dichromate as alcohols are oxidised?
Turns from orange to green
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Why can only aldehydes be further oxidised?
Because of the hydrogen atom on the carbonyl group
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What is Fehlings solution?
A solution that contains Cu2+ions and alkali
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What reducing agent is used to reduce carbonyl compounds back to the alcohol?
Sodium tetrahydridoborate
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What are aldehydes reduced to?
Primary alcohols
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What are ketones reduced to?
Secondary alcohols
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What is produced when hydrogen cyanide reacts with carbonyl compounds?
Cyanohydrins
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What are cyanohydrins?
Molecules with a CN and an OH group
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What is the name of the reaction of hydrogen cyanide with carbonyl compounds called?
Nucleophilic addition
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Is hydrogen cyanide a weak or a strong acid?
Weak acid
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What happens to hydrogen cyanide when it is added to an aqueous solution?
It partially disociates to form H+ ions and CN- ions
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What is the cyanide ion described as?
A nucleophile
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What would you see if butanal and butanone were each warmed seperately with acidified potassium dichromate?
Butanal would turn from orange to green. Butanone would stay the same colour.
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Give the formula and name for the alcohol that is oxidised to produce propanoic acid
Propan-1ol CH3CH2CH2OH
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What chemical test would you use to distinguish between propanal and propane?
React both compounds with acidified potassium dichromate solution or with Fehlings solution
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Other cards in this set

Card 2

Front

What is it about the aldehyde that gives them different properties to ketones?

Back

The presence of a hydrogen atom attached to the carbonyl group

Card 3

Front

How are aldehydes and ketones prepared?

Back

Preview of the front of card 3

Card 4

Front

What type of alcohol is an aldehyde?

Back

Preview of the front of card 4

Card 5

Front

What type of alcohol is a ketone?

Back

Preview of the front of card 5
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