Question

a start up company is trying to produce its own brand of antibacterial ointment. it decides to analyze a generic brand already on the market so that it can make suitable modification to the chemical composition. its known that the generic ointment contain benzoic acid( active ingredient), benzhydrol (the fixative) and anise, which add fragrance. you are a part of development team that wishes to separate these three substances in order to determine their relative proportions in the ointment, as well as to discover any inactive or unlisted constituents. some member of your team were able to isolate the inactive ingredient; However, NMR reveals that you still have a mixture of benzoic acid, benzhydrol, anisole left unseparated. as a member of team, you have been asked to do the following: 1. design an experiment to separate the following compounds from a mixture using any combination of purification techniques (TLC, column chromatography, Extraction and recrystallization) 2. carry out characterization studies such as melting point, IR, NMR to confirm that your purification was successful. 3. determine the percent recovery of the individual components of the mixture. mixture originally contained; 0.5g benzoic acid, 0.25g benzhydrol, 0.25ml anisole and 10ml diethyl ether.

Answer 1

The mixture can be separated as follows.

1) Add diethyl ether to it.

2) add aqueous saturated NaHCO3 solution and skake well. Benzoic acid reacts and forms sodium salt of acid which dissolves in water. Water layer is separated. Organic layer has benzhydrol and anisole.

3) Add diethyl ether to aqueous layer and acidify the aqueous layer with concentrated HCl to reprecipitate benzoic acid. Separate ether layer Add anhydroud MgSO4 to organic layer, filter and remove solvent to get benzoic acid.

4) the first organic layer with benzhydrol and anisol is treated with NaOH (aq) solution. Anisole reacts and forms sodium salt of anisole which goes in water. Separate the water layer. The organic layer now has only benzhydrol. Remove solvent and we get benzhydrol.

5) Add diethyl ether to water layer and acidify with HCl to reprecipitate anisol. Dry the organic layer with MgSO4 (anhy) and remove solvent to obtain ansiol.