Summary.
The mechanism of the keto-enol tautomerism of malonaldehyde was studied by ab initio methods using 6-21G** and 6-311G** basis functions at the HF level. Two separate mechanisms were examined: through-space proton transfer in the ω-shaped form and through-space proton transfer in a sickle-shaped form obtained from the ω form by rotation. The transition state structure of the ω form is non-planar, whereas that of the sickle form is planar. The sickle form is connected with a 2nd order saddle, indicating that there should exist a lower energy barrier, i.e. that the through-bond mechanism may be preferred. The calculated energy barriers of keto-enol tautomerism for the sickle form is twice as high as those for the omega form.
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Received January 18, 1999. Accepted (revised) August 4, 1999
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Delchev, V., Nikolov, G. Ab initio Study of the Keto-Enol Equilibriumof Malonaldehyde. Monatshefte fuer Chemie 131, 99–105 (2000). https://doi.org/10.1007/PL00010307
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DOI: https://doi.org/10.1007/PL00010307