Which statement is true about preparing Grignard reagents?

• A. They must be prepared under strictly anhydrous conditions in an ether solvent.
• B. They can be prepared in aqueous solvents with rapid reaction.
• C. They are stable in air.
• D. They are best prepared in protic solvents.

Answer: (A)

Grignard reagents are highly reactive organomagnesium species that form best under strictly anhydrous conditions in an ether solvent. Water, oxygen, or protic solvents will quench or destroy the reagent, because the Mg–C bond is extremely reactive with protons and moisture, yielding hydrocarbons and magnesium hydroxide or oxide. The ether solvent is crucial because its lone pairs coordinate to the magnesium, stabilizing the Grignard as a chelated complex and allowing formation and subsequent reactions to proceed. Because of this sensitivity, preparing Grignards in aqueous or protic environments or exposing them to air is not feasible, which is why the requirement for anhydrous conditions in an ether solvent is the correct description.