Organic synthesis
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What is the purpose of refluxing during the production of aspirin?
Igloo writes …
You may well have carried out the laboratory preparation of aspirin at your present school or college. If not, please refer to the description of this experiment in the Nuffield Students’ Book on pages 289-290.
The first stage of this preparation involves the reaction between 2-hydroxybenzoic acid and ethanoic anhydride. This reaction works well in the presence of a few drops of phosphoric acid (a catalyst). Even so, the rate of this reaction increases still further if the mixture is heated. To avoid any loss of harmful volatile components (e.g. ethanoic anhydride) from the mixture by evaporation, a reflux system is used to condense vapours escaping from the hot flask. After about 5 minutes of refluxing over a water bath, it can be assumed that the reaction is complete. At this stage the crude aspirin can be extracted from the mixture.
Risk assessment
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updated: 22 August 2003
