Grignard reagents (RMgBr) are highly reactive nucleophiles that react with carbon dioxide to form carboxylates. Upon hydrolysis, the carboxylate intermediate converts into a carboxylic acid. In this case, methyl magnesium bromide (CH$_3$MgBr) reacts with CO$_2$ to produce acetic acid (CH$_3$COOH). This reaction is widely used in organic synthesis for preparing carboxylic acids.