Which product is formed when CO2 is treated with methylmagnesium bromide followed by acidic workup?

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Multiple Choice

Which product is formed when CO2 is treated with methylmagnesium bromide followed by acidic workup?

The main idea is that a Grignard reagent reacts with carbon dioxide to give a carboxylic acid that has one more carbon than the R group of the Grignard. Here, the Grignard is methylmagnesium bromide, so R is CH3. When CH3− attacks CO2, a magnesium carboxylate forms: CH3COO−MgBr. After acidic workup, this is protonated to the carboxylic acid CH3CO2H, which is acetic acid. So the product is acetic acid. If you used ethylmagnesium bromide, you’d get propionic acid; with phenylmagnesium bromide you’d get benzoic acid.

The main idea is that a Grignard reagent reacts with carbon dioxide to give a carboxylic acid that has one more carbon than the R group of the Grignard. Here, the Grignard is methylmagnesium bromide, so R is CH3. When CH3− attacks CO2, a magnesium carboxylate forms: CH3COO−MgBr. After acidic workup, this is protonated to the carboxylic acid CH3CO2H, which is acetic acid. So the product is acetic acid. If you used ethylmagnesium bromide, you’d get propionic acid; with phenylmagnesium bromide you’d get benzoic acid.

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