Answer :
A Grignard reagent, specifically methylmagnesium halide, reacts with CO2 to initially form a magnesium carboxylate, which upon acid hydrolysis gives acetic acid as the final product.
When a Grignard reagent reacts with carbon dioxide (CO2), the reaction initially yields a magnesium salt of a carboxylic acid. The reaction sequence is as follows:
- The dry CO2 is bubbled through a solution of the Grignard reagent in ethoxyethane.
- The Grignard reagent adds to the carbon dioxide to form the magnesium carboxylate intermediate.
- Upon acid hydrolysis, typically using dilute sulfuric or hydrochloric acid, this intermediate is converted to a carboxylic acid.
Given that the end product is acetic acid (CH3COOH), the precursor Grignard reagent needs to have one less carbon atom. Therefore, the Grignard reagent must be methylmagnesium halide (CH3MgX).
The equation for the formation of acetic acid from methylmagnesium halide and CO2 is:
CH3MgX + CO2 → CH3CO2MgX
CH3CO2MgX + H2O + acid → CH3COOH + MgX(OH)
