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tests for alcohols

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
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.
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.
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.
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.

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