[screechy]

3. A solution of p-toluidine in 5% aqueous HCl is placed in a flask. An equal volume of the solvent diethyl ether is then added and the mixture is stoppered, shaken and then allowed to stand to reach equilibrium. Diethyl ether is immiscible with aqueous solvents, and the mixture forms two layers: a diethyl ether layer and an aqueous layer.

a) Which solvent forms the upper layer?
b) What does the aqueous layer contain?

5% aqueous NaOH is now carefully added in order to neutralise the mixture, then the flask is stoppered, shaken and then allowed to stand to reach equilibrium again.

c) Now, which solvent contains the p-toluidine?

Outline a procedure for separating a mixture of p-toluidine and naphthalene by exploiting their different solubilities.


I'm mainly just looking for help with the procedure and verifying that my current answers are valid. For part a I answered that diethyl ether would be on the top layer since the aqueous layer has hydrogen bonding, making it sink to the bottom despite that a water molecule is smaller and lighter. For b, I thought that water, HCl and Toluidine would be in the bottom layer since diethyl ether is immiscible and therefor would not form a homogenous mixture with the other substances.

For part c, I assumed the Toluidine would now be on the top layer with water and NaCl on the bottom aqueous layer due to the same reasoning used for part a.

Though for the procedure outline I'm a bit lost. Would I add HCl to separate the two layers? The top being naphthalene that just needs evaporation and the bottom with p-toluidine for further extraction. Then add NaOH to neutralize and extract the solution to extract P-toluidine with heat as well? Or am I completely reversed? Is diethyl ether needed? What purpose does it serve?

[AWK]

For a
compared density of ethyl ether and water (density of 5 % HCl is very close to that of water - d=1.025)
For b
Water phase contains toluidine hydrochloride and an excess of HCl
For c
 see a (for upper and lower layers). After neutralization toluidine forms solution with ether.

Check solution of naphtalene in water (and diluted HCl).