Question

1)When you perform a liquid-liquid extraction using a separatory funnel, which of the following organic solvent is on the bottom of the aqueous phase and which is on top? (write your answer by the solvent name) a) Ethyl acetate b) hexane c) Dichloromethane d) diethyl ether 2) If you are performing a liquid-liquid extraction and you have a mix of a carboxylic acid and a non-acidic compound, which combination of solvents would you use for the separation? a) dichloromethane/HCI b) dichloromethane/methanol c) dicholoromethane/NaOH d) NaOH and NaHCO3 - Why?

Answer 1

1) The density of dichloromethane is higher than that of the water and therefore, it will be in the bottom of aqueous phase. All other solvents ethyl acetate, hexane and diethyl ether are less denser that water therefore they will appear on the top.

2) The combination of solvent should be used is, c) dichloromethane/NaOH. As the the mixture contains carboxylic acid and a non acidic compound, after addition of NaOH the carboxylic acid will form a salt (sodium carboxylate) and will move from dichloromethane layer to NaOH layer. The non acidic compound however will still be in dichloromethane layer. This way we could separate acidic and non-acidic compound.