Question

A Grignard reaction is sensitive to many factors. Careful attention to details and precautions ate important to its success. Tell me:

a) Why we pre-polish or grind the Mg turnings before beginning.

b) Why it is necessary to oven dry, flame dry, or pre-rinse glassware with dry solvent before beginning the reaction.

c) Why a crystal of iodine may help get the reaction started.

d) Why the reaction vessel is fitted with a drying tube.

Answer 1

a) Why we pre-polish or grind the Mg turnings before beginning. --> so all oxidant is gone, we increase the area of rection

b) Why it is necessary to oven dry, flame dry, or pre-rinse glassware with dry solvent before beginning the reaction. We must avoid all kind of humidity of water droplets; it is pretty sensible to water

c) Why a crystal of iodine may help get the reaction started. --> Iodine will "clean" the surface/upper most layer, so only Pure Magnesium is available for the reaction

d) Why the reaction vessel is fitted with a drying tube. --> Once again, we need to dry all; we need to avoid all kind of moisture so our reaction does not deviates