Solubiity and extraction orgo question

[rocky90]

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Hi,

When we extract say benzoic acid from a mixture dissolved in ether we use a base such as bicarbonate which causes it to move to the aqueous layer. However, benzoic acid should be soluble in water in the first place since it is polar.

Thanks

 

[mario0923]

Hi,

When we extract say benzoic acid from a mixture dissolved in ether we use a base such as bicarbonate which causes it to move to the aqueous layer. However, benzoic acid should be soluble in water in the first place since it is polar.

Thanks

you are right that benzoic acid is polar but it has a big ring which makes it insoluble to water. wikipedia (if you trust it) says it is soluble in high temperature water and insoluble in cold water. So basically you can't use water for extracting benzoic acid.
Benzoic acid is soluble in NaOH, insoluble in HCl.

if you want to make sure you get look a "map" of organic compound solubity.

 

[n27s]

it helps when you think about it like this: benzoic acid is a weak acid, thus extracting it with a base will form a salt in water, making it soluble.

 

[rocky90]

I understand that part, but what bothers me is the extraction of some acid with a base. I agree it would deprotonate the acid to form an ion thus making it dissolve in the aqueous phase but the acid should have been soluble in water in the first place since it is polar. We can take any acid, not just benzoic for example. Is there a difference between being soluble and dissolving.