Question

purification of organic compound by crystallization ​

Answer 1

Heya Ma8

Recrystallization is a commonly employed method for the purification of organic solids. In the proper solvent, an organic compound can be dissolved to form a hot, saturated solution that, upon cooling, generates crystals in a pure form. The key to a good recrystallization is to find the proper solvent. The solvent should have the following properties:

• It should completely dissolve the desired compound when hot (usually at the boiling point of the solvent).

• It should dissolve very little of the desired compound when cold (usually after fifteen minutes in an ice/water bath).

• It should dissolve impurities at all temperatures or not at all.

• It should be unreactive toward the compound.

• It should dissolve the compound in a reasonable amount of solvent. Too much solvent

will make recrystallization extremely slow and the yield is likely to be low. Too little solvent will make it difficult to filter off all of the dissolved impurities when collecting crystals. As a rule of thumb, you might aim to find a solvent that will dissolve a gram of compound in ~5-10 mL of solvent.

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