Benzoic acid separation from benzyl alcohol

Figure 13.1 shows a flowchart for the separation of benzoic acid, a water-insoluble carboxylic acid, from benzyl alcohol, a water-insoluble nonacidic compound. First, we dissolve the mixture of benzoic acid and benzyl alcohol in diethyl ether. Next, we shake the ether solution with aqueous NaOH to convert benzoic acid to its water-soluble sodium salt. Then we separate the ether from the aqueous phase. Distillation of the ether solution yields first diethyl ether (bp 35 °C) and then benzyl alcohol (bp 205 °C). When we acidify the aqueous solution with HCl, benzoic acid precipitates as a water-insoluble solid (mp 122 °C) and is recovered by filtration. The ability to separate compounds based on their acid-base properties is very important in laboratory and industrial chemistiy. ... 

Flowchart for separation of benzoic acid from benzyl alcohol. 

Purpose. This experiment illustrates the simultaneous oxidation and reduction of an aromatic aldehyde to form the corresponding benzoic acid and benzyl alcohol. The experiment further demonstrates the techniques for separation of a carboxylic acid from a neutral alcohol. For a detailed discussion of this extraction procedure, see Experiment [4C]. 

Kg [HB W11039] 13H2O has been used as a precatalyst for the oxidation of alcohols in water at 90°C with H2O2 as the oxidant. Secondary alcohols such as cyclohexanol have been converted (99%) in 3 h to the corresponding ketones and separated from the aqueous phase by extraction. Due to the occurrence of an alcohoUc layered phase, benzyl alcohol has been oxidized in 98% conversion and 83% selectivity, without extensive over-oxidation to benzoic acid. ... 

At some point in the near future you should watch the video entitled Solvent Extraction — one organic in the multimedia activity Practical techniques on the Experimental techniques CD-ROM that accompanies this book. This activity deals with a case where the product to be extracted from the reaction mixture is that from a typical oxidation of a primary alcohol. Benzoic acid has been produced by the oxidation of benzyl alcohol with acidified potassium dichromate, and the organic product has to be separated from the remaining inorganic reagents. This activity should take approximately 10 minutes to complete. 

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