Answer :
Final answer:
The reaction between phenyl magnesium bromide and carbon dioxide forms a magnesium salt of benzoic acid, which upon acid hydrolysis yields benzoic acid.
Explanation:
The reaction between phenyl magnesium bromide and carbon dioxide is a two-step process which ultimately forms a carboxylic acid after acid hydrolysis. Initially, phenyl magnesium bromide reacts with carbon dioxide to yield a carboxylate intermediate, specifically, the magnesium salt of benzoic acid (PhCO2MgBr). Upon acid hydrolysis, this intermediate is converted into benzoic acid (PhCO2H), which is the final product of the reaction. During the reaction, dry carbon dioxide is bubbled through a solution of the Grignard reagent in ethoxyethane. The carbon which begins attached to the bromine in phenyl magnesium bromide acts as a nucleophile and attacks the electrophilic carbonyl carbon of carbon dioxide. After the addition of the Grignard reagent to the carbon dioxide, quenching the reaction with aqueous acid leads to the formation of the desired carboxylic acid.
