Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    14
    ReputationRep:
    hey all
    im aware you can use sodium carbonate to test for a carboxylic acid, but what about a aldehyde and ketone?
    would you just carry out the oxidation tests to identify if its a tertiary alcohol, as it would remain orange
    Then tollens or fehlings to work out if it is a ketone or aldehyde
    then oxidation again to work out if its aldehyde or carboxylic acid?
    thanks in advance
    Offline

    4
    ReputationRep:
    (Original post by AishaTara)
    hey all
    im aware you can use sodium carbonate to test for a carboxylic acid, but what about a aldehyde and ketone?
    would you just carry out the oxidation tests to identify if its a tertiary alcohol, as it would remain orange
    Then tollens or fehlings to work out if it is a ketone or aldehyde
    then oxidation again to work out if its aldehyde or carboxylic acid?
    thanks in advance
    Sodium metal will not react with a ketone or aldehyde as they lack the acidic groups necessary for such a reaction.

    However, carboxylic acids will react with Na metal.
    Offline

    17
    ReputationRep:
    (Original post by AishaTara)
    hey all
    im aware you can use sodium carbonate to test for a carboxylic acid, but what about a aldehyde and ketone?
    would you just carry out the oxidation tests to identify if its a tertiary alcohol, as it would remain orange
    Then tollens or fehlings to work out if it is a ketone or aldehyde
    then oxidation again to work out if its aldehyde or carboxylic acid?
    thanks in advance
    If you want to distinguish between a ketone and an aldehyde, just use Tollens' Reagent - you'll get a silver mirror with an aldehyde and no visible change with a ketone.

    With a carboxylic acid, you could also add a few drops of universal indicator; it would turn yellowy-orange, as it is a weak acid.
    Offline

    1
    ReputationRep:
    (Original post by AishaTara)
    hey all
    im aware you can use sodium carbonate to test for a carboxylic acid, but what about a aldehyde and ketone?
    would you just carry out the oxidation tests to identify if its a tertiary alcohol, as it would remain orange
    Then tollens or fehlings to work out if it is a ketone or aldehyde
    then oxidation again to work out if its aldehyde or carboxylic acid?
    thanks in advance
    2,4 Dinitrophenylhydrazine can be used to test for an aldehyde or ketone. The orange solution turns to an orange precipitate on the positive test.

    Not that this tests negative for carboxilic acids because of the resonance structure that is set up between the two oxygens bonded to the carbon.
    Offline

    4
    ReputationRep:
    To add to Lord or Ruin's post.... 2,4-DNPH will NOT differentiate between a aldehydes and ketones.

    A positive result (orange ppt.) is seen in both cases.
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    What newspaper do you read/prefer?
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Quick reply
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.