Extraction Question

[betterfuture]

A first year graduate student treats the below compound with aq. NaOH and heats the reaction for 1 hour. After cooling down the reaction, what must he do to isolate the desired carboxylic acid product?

Anybody know how to go about this problem?

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[salemstein]

Not 100% sure but I would add HCl to protonate the RCOO-? Then the product should go into the organic layer

 

[betterfuture]

Hey! Thanks for your response. That seems legit. However, do you know which one is the preferred layer to dissolve the product in? The organic or the aqueous? Also, why does the compound dissolve in the organic layer? Isn't this the nonpolar layer? How does changing the carboxylate to the carboxylic acid change it from polar-->nonpolar? It seems the carboxylic acid would still be polar.

 

[salemstein]

Carboxylate is more polar than Carboxylic acid because it is negatively charged. Look at the rest of the structure (the benzyl + carbonyl + alkanes). A majority of the molecule is pretty non-polar compared to the COOH part, so it will dissolve in organic.

 

[betterfuture]

Yeah. I guess I see how the charged molecule is more soluble in aqueous solution than the neutral form. I guess because the (-) charged on the carboxylate will participate with the bonding between aqueous molecules making it more soluble as opposed to the neutral compound that would be less soluble in the aqueous environment. Thanks! Makes sense now.