Grignard reagent is a very nucleophilic reagent in form of
organomagnesium halide and it converts carbonyl compounds into
alcohols.
The general solvent used is diethyl ether which is non-polar
and having no acidic hydrogen for the grignard to extract.
If instead ethanol or ethyl alcohol is used as a solvent, it
will deprotonate the alcohol abstracting the -H with it while
leaving the negatively charged oxygen of the alcohol.
The acidic proton will protonate the magnesium ion destroying
the grignard reagent for further reaction.