Recrystallization summary
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Recrystallization is a technique used to purify compounds by dissolving an impure sample in a minimum amount of hot solvent, allowing the solution to cool slowly so that the desired compound crystallizes while impurities remain in solution, then collecting and washing the crystals. There must be a difference in solubility between the compound and impurities for effective separation. Organic compounds are typically more soluble in hot solvents than cold, allowing crystallization upon cooling.
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Recrystallization summary
- 2. Key Ideas - In recrystallization, crude material is formed in the minimum amount of hot solvent. - The solution needs to cool slowly until one of the compounds within the solution recrystallizes while the other stays in liquid phase.
- 3. There must be a difference in solubility to separate the desired product from the impurities. • Typically organic compounds are more soluble in hot solvent than cold. • The compound being recrystallized should be dissolved in hot solvent but be insoluble in cold solvent. Remember: “like dissolves like” • Polar compounds dissolved in polar solvent, if the polarities are too similar the compound will dissolve but will not recrystallize.
- 4. Procedure for Recrystallization Choose a solvent Dissolve the solute in a minimum volume Decolorize & Filter All the system to cool slowly to crystallize solute Collect and wash crystals