| The formation of humins during acid-catalyzed hydrolysis of carbohydrates is believed to occur via aldol addition/condensation. However, levulinic acid appears to be stable at reaction conditions; its ketone group apparently does not participate in aldol chemistry to any significant extent as evidenced by the 1:1 stoichiometry of formed levulinic:formic acids. Experiments using added levulinic acid showed that the 1:1 stoichiometry is does not change with varying levulinic acid concentration. Separate experiments indicate that levulinic acid does form a unidentified products, believed to be lactones, at longer reaction times. Computational chemistry indicates that the lactones do not form from enols of levulinic acid. |
