Grignard reagent encountering water: what are the products?

Master NCEA Level 3 Organic Chemistry Reaction Schemes. Prepare with multiple choice questions, complete with hints and detailed explanations. Ace your exam with our comprehensive tools!

Multiple Choice

Grignard reagent encountering water: what are the products?

Grignard reagents are highly reactive with proton sources like water, acting as carbanions that grab a proton from the water. The proton transfer converts the carbon–magnesium bond into a C–H bond, giving the corresponding alkane, while the magnesium binds the hydroxide and halide from the salt. The overall result is RMgX + H2O → RH + Mg(OH)X. So you get the alkane and the magnesium hydroxide salt of the halide, not hydrogen gas as a separate product, not an aldehyde, and not a metal hydride. For example, phenylmagnesium bromide with water yields benzene and Mg(OH)Br. This is why the quench with water stops the Grignard reagent and yields RH and Mg(OH)X.

Grignard reagents are highly reactive with proton sources like water, acting as carbanions that grab a proton from the water. The proton transfer converts the carbon–magnesium bond into a C–H bond, giving the corresponding alkane, while the magnesium binds the hydroxide and halide from the salt. The overall result is RMgX + H2O → RH + Mg(OH)X. So you get the alkane and the magnesium hydroxide salt of the halide, not hydrogen gas as a separate product, not an aldehyde, and not a metal hydride. For example, phenylmagnesium bromide with water yields benzene and Mg(OH)Br. This is why the quench with water stops the Grignard reagent and yields RH and Mg(OH)X.

More practice questions