Recrystallization

is the primary method for purifying solid organic compounds.
Compounds obtained from natural sources or from reaction mixtures almost always contain
impurities

(1)How could we choose a good solvent :
• The solubility of the compound in the solvent used for recrystallization is
important
• A compound usually exhibits one of three general solubility behaviors:
(1)the compound has a high solubility in both hot and cold solvent,
(2) the compound has a low solubility in both hot and cold solvent,
(3)the compound has a high solubility in hot solvent and a low solubility in cold
solvent. Solvents which exhibit the first two behaviors are not useful for recrystallizing
a compound. A solvent showing the third behavior, that is, high solubility at high
temperatures and low solubility at low temperatures, is one that is suitable for use as a
recrystallization solvent.

(1)How could we choose a good solvent :
• The solubility of the compound in the solvent used for recrystallization is
important
• A compound usually exhibits one of three general solubility behaviors:
(1)the compound has a high solubility in both hot and cold solvent,
(2) the compound has a low solubility in both hot and cold solvent,
(3)the compound has a high solubility in hot solvent and a low solubility in cold
solvent. Solvents which exhibit the first two behaviors are not useful for recrystallizing
a compound. A solvent showing the third behavior, that is, high solubility at high
temperatures and low solubility at low temperatures, is one that is suitable for use as a
recrystallization solvent.

(1)How could we choose a good solvent :
• The solubility of the compound in the solvent used for recrystallization is
important
• A compound usually exhibits one of three general solubility behaviors:
(1)the compound has a high solubility in both hot and cold solvent,
(2) the compound has a low solubility in both hot and cold solvent,
(3)the compound has a high solubility in hot solvent and a low solubility in cold
solvent. Solvents which exhibit the first two behaviors are not useful for recrystallizing
a compound. A solvent showing the third behavior, that is, high solubility at high
temperatures and low solubility at low temperatures, is one that is suitable for use as a
recrystallization solvent.