Chemistry 223 Lab Report

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Chemistry 223 Lab ReportChromatography is a method of analyzing and purifying organic compounds based on polarity differences. Two different techniques used are flash column chromatography and thin ... layer chromatography (TLC). Flash column chromatography is used for the separation of large quantities of compounds under air pressure, whereas TLC is used for qualitative and small-scale separations. An essential principle of chromatography is the distribution equilibrium between a compounds mobile phase and the stationary phase. The mobile phase will be an organic solvent while the stationary phase is usually a polar surface, in this lab we used silica gel. The first part of this lab was to complete TLC plates of four compounds in solvents that vary in polarity. The solvents used were Hexanes and Ethyl Acetate. Then calculate the Rf -values for the four compounds. The Rf value is the distance traveled by the compound divided by the distance traveled by the solvent. The second part of this lab used column chromatography to separate a mixture using the same solvents, but gradually increasing its polarity by using a greater concentration of ethyl acetate to hexanes. We can then check how well the mixture was separated by comparing TLC of separated to the TLC of the pure compounds. Lastly, TLC chromatography was used to identify an unknown mixture containing two compounds of either acetylsalicylic acid (aspirin), phenacetin and caffeine. [Show More]

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