An Ideal Woman Essay

3700 WordsMay 7, 201315 Pages
Recrystallization. Recrystallization is the primary method for purifying solid organic compounds. Compounds obtained from natural sources or from reaction mixtures almost always contain impurities. The impurities may include some combination of insoluble, soluble, and colored impurities. To obtain a pure compound these impurities must be removed. Each is removed in a separate step in the recrystallization procedure. To understand the recrystallization process, solubility behavior must first be considered. It is often stated that "like dissolves like". More correctly, it should be stated that, "compounds having similar structural features will be soluble in one another". Some obvious structural features that may affect solubility include polarity and the ability to hydrogen bond. For example, a compound having just a few carbons and an alcohol functional group (FG) would be expected to be soluble in solvents that have a few carbons and an alcohol FG or in some other polar solvent, and to be less soluble in nonpolar solvents. Conversely an alkane would be expected to show the opposite solubility behavior. In most cases though it is not as simple as this. If for example a compound has lots of carbons and hydrogens (> 6 C's) and just one alcohol group, the solubility will be dominated more by the alkyl part of the molecule than by the alcohol part, and the compound will show a solubility behavior more like that of an alkane. For known compounds it is useful to consider the structure of the compound when choosing a recrystallization solvent. An educated guess can save some time. Usually however, the structure of a compound may not be known so the solvent must be chosen by carrying out solubility tests. The first part of this experiment involves carrying out solubility tests on known compounds. Later on such solubility tests will be used to find a suitable

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