Grignard Reaction?

Question

Why do we need ether to form a grinard reagent? More specifically, why does it need to be anhydrous ether?

Reaction Example:

Ar-Br + Mg, ether = Ar-MgBr
(Ar is an aromatic ring)

Answer 1

We need ether, because nothing else seems to work. It must be anhydrous because:

Ar-MgBr + H2O ===> ArH + Mg++ + Br- + OH-

Answer 2

Aluminum will engage in unwanted side reactions if there is water present. A Grignard reagent can be used with alkanes as well as aromatics.