What would occur if we used wet solvent in a Grignard reaction?

1 Answer
Dec 29, 2017

Reduced yield.....

Explanation:

The Grignard reagent is a powerful nucleophile, and a powerful base. The use of wet ether or wet THF would result in difficulty in forming the Grignard reagent....

#R-X + Mgstackrel(Et_2O)rarrR-MgX#

#R-MgX + H_2O rarr R-H + MgX(OH)#..

Sometimes we form the Grignard reagent and quench it with #D_2O#, i.e. #""^2H_2O#, to give a labelled hydrocarbon, which we may use in a separate experiment....

#R-MgX + ""^(2)H_2O rarr R-""^(2)H + MgX(O""^2H)#

As a practical tip, when you start out making Grignard reagents, you often go to absurd lengths in drying your solvents. Now Grignards are water-sensitive, but they are a bit more robust than you might think... I used to make molar quantities of Grignards with diethyl ether that had dried over molecular sieves, and used straight out of the bottle.