Which of the following does NOT convert methylmagnesium bromide, CH3M…

The correct answer is Option (4) → Diethyl ether

A Grignard reagent is highly reactive and reacts with any source of proton to give a hydrocarbon. Water, alcohols and amines are acidic enough for this, so each turns CH₃MgBr into methane. A compound with no such hydrogen does not.

Option (1) Water — Converts CH₃MgBr into methane. The H of the O–H group is taken up by the methyl group:

    \( \displaystyle \ce{CH3MgBr + H2O -> CH4 + Mg(OH)Br} \)

Option (2) Ethanol — Converts CH₃MgBr into methane. An alcohol has an acidic O–H hydrogen:

    \( \displaystyle \ce{CH3MgBr + C2H5OH -> CH4 + Mg(OC2H5)Br} \)

Option (3) Ethanamine — Converts CH₃MgBr into methane. A primary amine has N–H hydrogens that are acidic enough:

    \( \displaystyle \ce{CH3MgBr + C2H5NH2 -> CH4 + Mg(NHC2H5)Br} \)

Option (4) Diethyl ether — Does not convert CH₃MgBr into methane. Diethyl ether, C₂H₅–O–C₂H₅, has no O–H or N–H hydrogen. This is why Grignard reagents are prepared in dry ether, kept free of even traces of moisture.

NCERT (2026-27 edition):
6.7.1 Reactions of Haloalkanes – “…These reagents are obtained by the reaction of haloalkanes with magnesium metal in dry ether.” … “Grignard reagents are highly reactive and react with any source of proton to give hydrocarbons. Even water, alcohols, amines are sufficiently acidic to convert them to corresponding hydrocarbons.”

“It is therefore necessary to avoid even traces of moisture from a Grignard reagent. That is why reaction is carried out in dry ether.”