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3-SalicylicacidF06

3-SalicylicacidF06 - Unexpected Result from Extraction and...

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Unexpected Result from Extraction and Analysis of Aspirin and Caffeine from Anacin Many of you reported to me that the melting point range of your isolated “aspirin” was approximately 20 o C above the reported range. In general, you know that a depressed melting point range signals an impure product. A range a few degrees (~1-5 o C) above the normal range could be accounted for by an improperly calibrated thermometer or heating the sample too quickly. However, a range 20 o C above the expected value signals that the sample is not what you thought it was. The ranges reported to me were right around 158-161 o C, which is in perfect agreement with the literature value for salicylic acid. Most likely, during the isolation experiment when the aspirin was heated in water at a very low pH (step 4b) the aspirin was hydrolyzed to give salicylic acid (see equation below). You will learn the details of this reaction in Chem 152 – though if you are interested I have posted the mechanism of the reaction as well. You are not responsible
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