I need to separate a three compound mixture containing a base (2-naphthol or phe
ID: 859387 • Letter: I
Question
I need to separate a three compound mixture containing a base (2-naphthol or phenol), a carboxylic acid (salicylic or benzoic), and a neutral compound (biphenyl or naphthalene). I will be dissolving the compound in diethyl ether then using a separatory funnel to extract each compound. Will HCl be able to extract the base? I was planning on using NaOH to extract the acid. I also have the choice of using NaHCO3. Should there be a specific extraction order? Is it necessary to make the basic extract more basic by adding NaOH?
Explanation / Answer
The mixture of phenol, carboxylic acid and neutral compound can be separated as follows:
1. Dissolve all the three in diethyl ether.
2. Wash diethyl ether with saturated sodium bicarbonate solution, so that carboxylic acid gets extracted in sodium bicarbonate solution as sodium salt. Separate bicarbonate solution and recover carboxylic acid by acidifying aqueous solution with dilute hydrochloric acid and extrating it in organic solvent.
3. Now the diethyl ether layer contains phenol and neutral compound. Extract it with sodium hydroxide solution. The phenol forms sodium salt and gets extracted in sodium hydroxide solution. Separate this aqeous solution and recover phenol by acidifying it will dilute hydrochloric acid and extracting phenol in organic solvent.
4. Now diethyl ether contains only neutral compound. Evaporate diethyl ether to get neutral compound.
5. Phenols are not basic, hence, they will not get extracted in dil HCl, as mentioned in the question.