Question

Grignard reaction questions?

a. Ethanol is often present in solvent-grade diethyl ether. If this grade, rather than anhydrous were used, what effect would the ethanol have on the formation of the Grignard reagent?

b. Why is it necessary to acidify the mixture (addition of HCl) after the completion of Grignard reaction?

c. Why is it necessary to clean and cut the magnesium ribbon into small pieces in the preparation of Grignard reagent?

Thank you

Answer 1

a) The Grignard reagent formed would be destroyed by its reaction with ethanol

Grignard reaction carried out in an anhydrous solvent. Because the Grignard reagent formed would be destroyed by its reaction with water present in a non-anhydrous solvent. water present will convert the Grignard reagent to R-H.

b) Dilute hydrochloric acid is added to the reaction mixture to protonate the salts, as well as to dissolve the magnesium salts

c) the reaction takes place on the surface of the metal. The reaction proceeds through single electron transfer