Self‐catalyzed keto‐enol tautomerization of malonic acid

Abstract

We demonstrate through quantum chemical calculations that the keto‐enol tautomerization of malonic acid can be catalyzed by the two tautomers of malonic acid itself. This self‐catalyzed process proceeds with a relatively low barrier (Gibbs energy ca. 13 kcal/mol in gas phase, 20 kcal/mol in aqueous phase), and involves the concerted transfer of two protons between the substrate and the carboxylic acid functionality of the malonic acid catalyst. This mechanism is expected to compete with the proton relay mechanism currently favored to explain the tautomerization of malonic acid in aqueous media. Malonic acid is an important constituent of secondary organic aerosol where the present chemistry may play a role in determining chemical composition.

Red Carbon: a Carbon-Oxygen-based covalent semiconductor for selective amine sensing

“…Furthermore, as it was previously reported, pure MA, at about the operating temperature, undergoes thermal β-decarboxylation via rearrangement in a cyclic six-membered transition state to acetic acid and CO2. [36][37][38] After the thermal treatment, the glass substrate is successfully coated with an deep-red film, which resembles the color described in previous reports on red carbon materials. 18,[39][40] Surprisingly, to the best of our knowledge, the optical absorption and emission properties were reported only once by Yang et al which however are considered not comparable due to the unusual low temperatures conditions used (140°C).…”

Direct Measurements of Covalently Bonded Sulfuric Anhydrides from Gas-Phase Reactions of SO3 with Acids under Ambient Conditions

“…Malonic acid is prone to undergo keto–enol tautomerism, forming a distinct structural isomer with only one −C­(O)­OH group (i.e., the enol form). The formation of an enol form of malonic acid can be self-catalyzed and can be stabilized by water molecules. − Since the enolic form of malonic acid has only one acid functionality, the formation of MDSA could be susceptible to the formation of the enol form. It could be seen in the mass spectra of the OA-SO 3 system (Figure B) that the signal intensity of deprotonated ODSA is nearly 25 times lower than deprotonated OMSA and in the case of the MA-SO 3 system, the intensity of the primary product (MMSA) is itself low and therefore the secondary product, i.e., MDSA was not detected.…”