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hydrolysing esters

i'm trying to find a test for esters, i've decided to heat under reflux with sodium hydroxide.

what is confusing me is would i get the salt (eg sodium ethanoate) or the acid (eg ethanol)

if i then add sulphuric acid apparently a white precipiate forms, why is this so?
You will get sodium ethanoate - if you use acid hydrolysis you get the free acid.

You may be getting sodium sulphate which isn't very soluble?
Reply 2
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lils270391
OP
but apparently adding sulphuric acid is meant to prove that the compound was origionally an ester
By adding acid you are turning a sodium salt back into an organic compound, depending on the identity of the original ester it may or may not fall out of solution (i.e. not soluble in water) giving you a solid...this is what you could be describing
Which ester are you hydrolysing?

If the ester were ethyl benzoate then you would get a white precipitate after hydrolysis and addition of acid...
Reply 5
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lils270391
OP
it's unknown, i need to prove the compound is an ester
The simplest 'test' for an ester is really the lack of positive results from other tests.
Reply 7
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lils270391
OP
could i test for the ester by refluxing it in dilute acid and then testing for a carboxylic acid with litmus paper? or is this too vague?
Reply 8
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lils270391
OP
infact, does it not have to be under relux? can i hydrolyse at room temperature with a stong acid cataylst (HCl??)
lils270391
could i test for the ester by refluxing it in dilute acid and then testing for a carboxylic acid with litmus paper? or is this too vague?


No, the solution you would use will always be acidic

infact, does it not have to be under relux? can i hydrolyse at room temperature with a stong acid cataylst (HCl??)


No
Reply 10
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lils270391
OP
ok so could i instead add sodium carbonate and check for effervescence to identify the carboxylic acid?
lils270391
ok so could i instead add sodium carbonate and check for effervescence to identify the carboxylic acid?


If you use acid hydrolysis then you are always going to have acid in the solution, hydrolysis or not - the 'sodium carbonate test' is for acids, not only carboxylic acids.
This thread topic has become an old chestnut.

"How can I test for an ester?"

The answer is always the same, as EVS rightly says 'there is no specific test for an ester'....

Believe him, he knows what he is talking about! :yep:

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