Purification and Thin-Layer Chromatographic Analysis of Caffeine

Topics: Solvent, Organic compound, Oxygen Pages: 4 (1241 words) Published: November 7, 2012
Purpose of the Experiment:
The intention of the experiment is to use solvent extraction methods to separate a mixture containing a carboxylic acid and a neutral compound. Once recovered, the solids were purified by recrystallization and examined by thin-layer chromatography, and their identities were derived by melting point and infrared (IR) spectroscopy. Extraction is a procedure that selectively dissolves one or more of the mixture compounds into a proper solvent. Extraction refers to the moving of compounds from one liquid solvent to another liquid solvent. A compound can be disconnected from impurities in a solution by extracting the compound from the first solvent into a second solvent. The compound must be more soluble in the second solvent than in the first solvent, and the impurities must be insoluble in the second solvent. Also the two solvents must not be soluble in one another because they need to produce two separate layers. The two layers are shaken to mix. This mixing helps the moving of the dissolved compound from one layer to another. Once the transfer procedure is finished, the layers form again. This time the separated layers separate the desired compound from the impurities. Washing is the reverse procedure, in which the impurities are moved to the second solvent, leaving the sought after compound in the first solvent. The aqueous, carboxylic acid, solvent used is polar and the organic, ether, solvent is non-polar. The more dense solvent is the bottom layer. In this case the aqueous water is on the bottom layer and the ether is on the top. Density is one way to differentiate each layer but the identities still have to be confirmed. A general rule of solubility is like dissolves like. Non-polar compounds, most organic compounds, are more soluble in non-polar solvents than in polar solvents. Ionic and polar compounds are more soluble in polar solvents like water. Ionic forms of the organic compound can be produced by...
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