Question

1) Why is methanol a good solvent for recrystallization of cholesterol?  
2) What chemical differences are needed between extraction solvent and re-crystallization solvent?

Answer 1

SOLUTION:

1.methanol is a good solvent for recrystallization of cholesterol because of Methanol can be used as a solvent for re-crystallization. A good solvent for re-crystallization is one in which impurities are more soluble than the compound which is to be dissolved when the solvent is hot. When the solvent is cooled the impurities must stay soluble while the compound precipitates.

when it compared to another solvents 2-butanone, hexane then it

Polarity and intermolecular forces play a key role in solubility. Since cholesterol is an organic compound it is soluble in organic solvents which are non-polar ( 2 - butanone) and the intermolecular forces are of the same order in 2-butanone as that of Cholesterol.

Cholesterol would be soluble in hexane but not highly soluble due to the difference in order of intermolecular forces.

2.

Chemical differences between extraction solvent and re-crystallization solvent is the compound should dissolve in the solvent at boiling point in case of recrystallization which is not necessary for extraction solvent which occurs at a particular temperature.