Question

POST LAB QUESTIONS-USE GOOGLE SCHOLAR TO HELP FIND THE ANSWERS 1) How would you pick the good solvent for the recrystallization of your chemical? 2) List ten solvents used mostly for recrystallization. Provide in the table physical properties for these solvents that help choosing the best solvent. 3) Why do we use a very cold solvent to wash crystals? 4) Why is it preferable to use vacuum filtration and not regular one for recrystallization?

Answer 1

1) A good solvent for the recrystallization of your chemical is the one which completely solubilizes your chemical and whose boiling temperature should not be very high.

For example, acetonitrile whose boiling point is 82 ^oC, which is not very high.

2) i) hexane

ii) diethyl ether

iii) toluene

iv) tetrahydrofuran

v) dichloromethane

vi) acetonitrile

vii) acetone

viii) pentane

ix) methyl t-butyl ether

x) methanol

3) A very cold solvent should be used to wash crystals in order to decrease their solubility in the washing solvent.

4) If you use regular filtration, which may take more time that solubilizes the crystals, which is unwanted. Hence, you need to prefer vacuum filtration.