It has been shown by 1H
and 13C NMR spectroscopy that 2-mercaptobenzoyl-hydrazones of aliphatic
and aromatic aldehydes exist in solution as tautomeric mixtures of linear and
cyclic benzo-1,3,4-thiadiazepine forms. The linear hydrazone form is
represented by (E,E')-and (E,Z')-conformational
isomers, differing in the disposition relative to the amide C–N bond. Growing bulk
of the alkyl substituent at the C=N bond of the aliphatic aldehydes derivatives
decreases the fraction of the cyclic tautomer; therewith the logarithms of the
constants of the chain-ring tautomeric equilibrium correlate with the ES steric constants of the
alkyl substituents. In the series of the aromatic aldehydes 2-mercaptobenzoylhydrazones
the linear tautomer prevails, and the logarithms of the tautomeric equilibrium
constants KT correlate
with the σ-constants
of the substituents in the aromatic nucleus.
Cite this paper
Ershov, A. Y. , Lagoda, I. V. , Vasileva, M. Y. , Yakimovich, S. I. , Chernitsa, B. V. , Kuleshova, L. Y. , Pavlova, L. V. and Yakimansky, A. V. (2017). Ring-Chain Tautomerism of the Condensation Products of 2-Mercaptobenzohydrazide with Aliphatic and Aromatic Aldehydes: Influence of Electronic and Steric Factors. Open Access Library Journal, 4, e3584. doi: http://dx.doi.org/10.4236/oalib.1103584.
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