A chemist wishes to separate a mixture of p-aminobenzoic acid (contains both an…
CHEMISTRY · Single correct · A Level · Chemistry · Chromatography · Chromatography
Problem
A chemist wishes to separate a mixture of p-aminobenzoic acid (contains both an acidic carboxyl group and a basic amino group), phenol (weak acid), and toluene (neutral) using the fewest possible liquid-liquid extraction steps. Which of the following procedures will isolate each compound in a different layer before any recrystallization or evaporation steps?
(a) Extract the mixture with dilute NaOH to deprotonate both acids. 2. Acidify the resulting aqueous layer with dilute HCl, assuming only p-aminobenzoic acid will precipitate while phenol stays in water, leaving toluene in the original organic layer.
(b) Extract the mixture with NaHCO3 solution to deprotonate both the carboxylic and phenolic groups. 2. Acidify the aqueous layer to recover p-aminobenzoic acid, assuming phenol will remain in the aqueous phase, leaving toluene in the organic layer.
(c) Extract the mixture with dilute HCl to protonate and dissolve p-aminobenzoic acid’s amino group. 2. Extract the remaining organic layer with dilute NaOH to deprotonate phenol, leaving toluene in the organic layer.
(d) Extract the mixture with saturated NaCl solution to “salt out” toluene. 2. Extract the remaining solution with dilute HCl to transfer p-aminobenzoic acid to water, leaving phenol in the original layer.