In the following chemical reaction, the major product obtained will be:
RMgBr + D2O →
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → RD
The alkyl group of a Grignard reagent takes up an acidic hydrogen from water:
\( \displaystyle \ce{R-MgX + H2O -> R-H + Mg(OH)X} \)
With heavy water (D2O) the alkyl group picks up deuterium instead of hydrogen:
\( \displaystyle \ce{R-MgBr + D2O -> R-D + Mg(OD)Br} \)
So the major product is RD, a deuterated hydrocarbon.
Why the other options are incorrect
Option (2) RH — Incorrect. This forms with ordinary water (\( \ce{H2O} \)); D2O supplies deuterium, not hydrogen.
Option (3) ROD — Incorrect. The carbanion takes up D from D2O; no oxygen becomes attached to the alkyl group.
Option (4) ROH — Incorrect. Alcohols are made from Grignard reagents by adding them to carbonyl compounds and then hydrolysing, not by reaction with water.
NCERT (2026-27 edition):
Reactions of Haloalkanes – …
