Kinetics and Thermodynamics of Tautomerization Reactions of 1,1‐ and 1,2‐Ethenediols

Tautomerism is a common phenomenon amongst organic molecules with easily interconvertible isomers, which can impact drug action and toxicity. Here we are interested in the enols of carboxylic acids, which are known to be much less stable than their acid counterparts. We are concerned primarily with hydrogen‐atom transfer reactions or keto enol tautomerism in ethenediols leading to acetic acid or glycoaldehyde and in particular the chemical kinetics at low temperatures where quantum mechanical tunneling plays a key role in the rates of reaction. We consider both the direct tautomerization reactions and those that are mediated by a water molecule, where the hydrogen transfer is facilitated by the formation of a low energy pre‐reaction complex, and we present energy barriers for conformer isomerizations and hydrogen transfer reactions. We provide thermochemical data, including heats of formation, standard entropy, heat capacity, and enthalpy change for all isomeric forms of molecules under investigation.