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Thermal solid-state Z/E isomerization of 2-alkylidene-4-oxothiazolidines: effects of non-covalent interactions

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Author(s): ZDRAVKO DŽAMBASKI | MILOVAN STOJANOVIĆ | MARIJA BARANAC-STOJANOVIĆ | DRAGICA M. MINIĆ | RADE MARKOVIĆ

Journal: Journal of the Serbian Chemical Society
ISSN 0352-5139

Volume: 76;
Issue: 3;
Start page: 317;
Date: 2011;
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Keywords: 4-thiazolidinones | solid-state isomerisation | non-covalent interactions | dynamic 1H-NMR spectroscopy

ABSTRACT
Configurational isomerization of stereo-defined 5-substituted and unsubstituted 2-alkylidene-4-oxothiazolidines (1) in the solid state, giving the Z/E mixtures in various ratios, was investigated by 1H-NMR spectroscopy, X-ray powder crystallography and differential scanning calorimetry (DSC). The Z/E composition can be rationalized in terms of non-covalent interactions, involving intermolecular and intramolecular hydrogen bonding and directional non-bonded 1,5-type S×××O interactions. X-Ray powder crystallography, using selected crystalline (Z)-4-oxothiazolidine substrates, revealed transformation to the amorphous state during the irreversible Z®E process. A correlation between previous results on the Z/E isomerization in solution and now in the solid state was established.
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