When a carboxylic acid reacts with a carbonate, which of the following describes the products?

• A. A ketone and water
• B. A salt of the carboxylate, carbon dioxide and water
• C. An ester and carbon dioxide
• D. A salt of the acid and hydrogen gas

Answer: (B)

Carboxylic acids react with carbonates as an acid–base reaction that releases a gas and forms a salt. The acid donates protons to the carbonate, converting the carbonate into carbon dioxide and water, while the carboxylate that remains pairs with the metal cation from the carbonate to give a salt of the carboxylate. A typical balanced form is 2 RCOOH + Na2CO3 → 2 RCOONa + CO2 + H2O. So the products are a carboxylate salt, carbon dioxide, and water. This differs from forming a ketone or an ester, and hydrogen gas isn’t produced in this reaction.