Analytical and chemical tests for Carbonyls and Carboxylic acids

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  • Created by: Hannah
  • Created on: 03-09-14 11:32
What is the chemical name for Brady's reagent?
2,4-Dinitrophenylhydrazine (2,4-DNPH)
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What observation would you see when Bradys is added to a molecule with a carbonyl group?
Forms a bright orange precipitate
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What would you see when you add Bradys to a caboxylic acid? Why?
Nothing. Carboxylic acids dont have carbonyl groups, therefore Bradys only tests for aldehydes and ketones
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How can you distinguish between an aldehyde and ketone once the precipitate has formed?
Each different carbonyl compound produces a crystaline derivative with a different melting point. Measure melting point and compare against known values
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What does Tollens' reagent identify?
It distinguishes between an aldehyde and a ketone
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How can an aldehyde be identified by Tollens'?
Heated in a tube with the aldehyde a silver mirror forms. The aldehyde is oxidised into a carboxylic acid and silver ions are reduced
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What is the half equation for this reaction?
Ag+(s) + e- -> Ag(s)
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Why doesn't Tollens work for ketones?
The only way to oxidise a ketone would be to break the C-C bond - aren't easily oxidised
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What is the reaction of carboxylic acids with more reactive metals?
Forms a salt of carboxylic acid (end in oate) and produces hydrogen
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What is the equation for ethanoic acid and magnesium?
2CH3COOH(aq) + Mg(s) -> (CH3COO)2Mg(aq) + H2(g)
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What is the reaction of a carboxylic acid with carbonates?
Form a salt, carbon dioxide and water
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What is the equation for ethanoic acid and sodium carbonate?
2CH3COOH(aq) + Na2CO3(s) -> 2CH3COONa(aq) + H20(l) + CO2(g)
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How are carboxylic acids neutralised?
With metal oxides and hydroxides to form salt and water
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What is the equation for ethanoic acid and magnesium oxide?
2CH3COOH(aq) + MgO(s) -> (CH3COO)2Mg(aq) + H2O(l)
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Other cards in this set

Card 2

Front

What observation would you see when Bradys is added to a molecule with a carbonyl group?

Back

Forms a bright orange precipitate

Card 3

Front

What would you see when you add Bradys to a caboxylic acid? Why?

Back

Preview of the front of card 3

Card 4

Front

How can you distinguish between an aldehyde and ketone once the precipitate has formed?

Back

Preview of the front of card 4

Card 5

Front

What does Tollens' reagent identify?

Back

Preview of the front of card 5
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