Question

Separation scheme for isolating benzoic acid
Could you please show me a separation scheme for isolating benzoic acid from a reaction mixture if mixing a Grignard reagent phenylmagnesium bromide with dry ice (CO2) in ether? Thanks!

Answer 1

Both benzoic acid and triphenyl are organic solutes, and therefore will dissolve in organic solvents. (ie: diethyl ether)

Benzoic acid (an acid) will react with a strong base (ie: NaOH) to form sodium benzoate (which is a water soluble salt) and aqueous NaCl.

Therefore, if you have a mixture of triphenyl and benzoic acid, you can dissolve it in an organic solvent (say diethyl ether) and add NaOH, to convert benzoic acid into a water soluble salt. (water is NOT soluble in organic solvents). therefore your mixture in solution will separate into two layers. The upper organic layer will contain triphenyl dissolved in ether, and the lower aqueous layer will contain the water soluble salt of benzoic acid and water. (as well as aqueous NaCl).

Using a separatory funnel, or other separation equpiment, the two layers can be separated.