What are the general products of a Grignard reaction with water, alcohols, or other proton sources?

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Multiple Choice

What are the general products of a Grignard reaction with water, alcohols, or other proton sources?

When a Grignard reagent (RMgX) meets a proton source such as water, an alcohol, or any acid, the Mg–C bond is protonated. This transfers the alkyl (or aryl) group to form the corresponding alkane RH, while the metal binds the conjugate base of the proton source to give the magnesium salt MgX(OH) or MgXOR. With a simple proton source like water, the typical products are RH and Mg(OH)X; with an alcohol, you’d get RH and Mg(OR)X. The option shown captures this general outcome by giving an alkane plus the magnesium salt of the conjugate base of the proton source (a common example being RH and Mg(OH)Br for a Grignard made from RMgBr). The other possibilities correspond to different chemistry: carboxylic acids would arise in different contexts (e.g., reactions with CO2), and ketones or secondary alcohols come from reactions of Grignards with carbonyl compounds, not from simple protonation.

When a Grignard reagent (RMgX) meets a proton source such as water, an alcohol, or any acid, the Mg–C bond is protonated. This transfers the alkyl (or aryl) group to form the corresponding alkane RH, while the metal binds the conjugate base of the proton source to give the magnesium salt MgX(OH) or MgXOR. With a simple proton source like water, the typical products are RH and Mg(OH)X; with an alcohol, you’d get RH and Mg(OR)X. The option shown captures this general outcome by giving an alkane plus the magnesium salt of the conjugate base of the proton source (a common example being RH and Mg(OH)Br for a Grignard made from RMgBr). The other possibilities correspond to different chemistry: carboxylic acids would arise in different contexts (e.g., reactions with CO2), and ketones or secondary alcohols come from reactions of Grignards with carbonyl compounds, not from simple protonation.

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