Which statement correctly describes Grignard reagents reacting with proton sources?

• A. It yields a Grignard byproduct.
• B. It yields an alkane (RH) and Mg(OH)Br.
• C. It yields a ketone.
• D. It yields an alcohol.

Answer: (B)

Grignard reagents are highly reactive with proton sources, so the carbon attached to magnesium is protonated. The hydrogen from the proton source ends up on that carbon, giving the corresponding alkane (RH). At the same time, the Mg–X bond goes with the oxide/hydroxide from the proton source, forming Mg(OH)X. The overall outcome is RMgX + H2O or ROH → RH + Mg(OH)X. This is why the hydrocarbon plus magnesium hydroxide salt is produced, matching the described products. A ketone would only form if a carbonyl compound were present to react with the Grignard, and an alcohol would require different steps or reagents, not just a simple proton quench.