2, 4-Dinitrophenylhydrazine is frequently used for making derivatives of ketones and aldehydes because the products (2, 4-dinitrophenylhydrazones, called 2, 4-DNP derivatives) are even more likely than the phenylhydrazones to be solids with sharp melting points. Propose a mechanism for the reaction of acetone with 2, 4-dinitrophenylhydrazine in a mildly acidic solution.