1,1-Ethenediol – The Long Elusive Enol of Acetic Acid

Artur Mardyukov, André K. Eckhardt, and Peter R. Schreiner
Angew. Chem. Int. Ed. 2020, 58, 5577–5580. DOI: 10.1002/anie.201915646

We present the first spectroscopic identification of hitherto unknown 1,1‐ethenediol, the enol tautomer of acetic acid. The title compound was generated in the gas phase through flash vacuum pyrolysis of malonic acid at 400 °C. The pyrolysis products were subsequently trapped in argon matrices at 10 K and characterized spectroscopically by means of IR and UV/Vis spectroscopy together with matching its spectral data with computations at the CCSD(T)/cc‐pCVTZ and B3LYP/6–311++G(2d,2p) levels of theory. Upon photolysis at λ=254 nm, the enol rearranges to acetic acid and ketene.