PhMgX

PhMgX, or phenylmagnesium halide, is a Grignard reagent in which a phenyl group (Ph) is bonded to magnesium coordinated to a halide (X = Cl, Br, or I). It functions as a highly reactive nucleophile and base, enabling the formation of new carbon–carbon bonds in organic synthesis. Common examples are phenylmagnesium chloride (PhMgCl) and phenylmagnesium bromide (PhMgBr).

Preparation and handling of PhMgX require strictly anhydrous conditions. They are prepared by inserting magnesium metal into phenyl halides (PhX) in dry ether solvents such as diethyl ether or tetrahydrofuran (THF) under inert atmosphere. The resulting solution is reactive toward moisture, oxygen, and many functional groups, and is typically stored under an inert gas in dry solvents.

In solution, PhMgX behaves as a polar organomagnesium species. It is highly reactive toward water and air, rapidly hydrolyzing to benzene and magnesium hydroxide halide (PhMgX + H2O → PhH + Mg(OH)X). The ether solvent coordinates to magnesium, stabilizing the reagent but also making it more reactive toward a wide range of substrates.

Reactions and applications of PhMgX center on carbon–carbon bond formation. It adds to aldehydes and ketones to yield secondary or tertiary alcohols after acidic workup; with formaldehyde it affords primary benzylic alcohols; with carbon dioxide it forms benzoic acid after hydrolysis; and it can react with epoxides to produce alcohols upon workup. Grignard reagents are also used to form alkanes or to couple aryl groups in multistep sequences.

Safety and handling emphasize moisture- and air-sensitivity, flammability of solvents, and exothermic hydrolysis. Reagents are typically prepared and used under inert atmosphere in dry laboratories.