Organic 2 Review Problem 30

Organic 2 Review Problem 30 - 14 PRACTICAL ORGANIC...

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14 PRACTICAL ORGANIC CHEMISTRY main product, and therefore will always eventually be left in the mother- liquor. Consideration will show that this assumption is not necessarily made: the assumption actually made is that the impurities are either more soluble than the main product, or, if less soluble, are present in such small proportion that in spite of the comparative solubilities they will be eliminated by recrystallisation. The two cases may be exempli- fied thus. Suppose the crude mixture contains 97% of the required compound A, and 3% of an impurity B. Then if (1) A is less soluble in a given solvent than B. It is clear that repeated recrystallisation will rapidly leave B entirely in the mother-liquors, and thus provide a pure sample of A. (2) A is more soluble in the solvent than B. Suppose that a given volume of the solvent when cold can dissolve 15 g. of A and 5 g. of B. If ioo g. of the crude product are dis- solved in this volume of the hot solvent, and the solution allowed to
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This note was uploaded on 09/19/2011 for the course CHM 2211 taught by Professor Castalleano during the Fall '06 term at University of Florida.

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