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Dynamic Behaviour of Cyclic Thiohydroxamic Acid Derivatives Barrier to Rotation about N2O Bonds in 4-Substituted N-Isopropoxythiazole-2(3H)-thiones and N-Isopropoxypyridine-2(1H)-thione
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1  Institut für Organische Chemie der Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany

Abstract: Activation parameters [DG200, DH2, DS2] for barriers to rotation about N2O bonds in N-isopropoxypyridine-2(1H)-thione (1) and two 4-substituted N-isopropoxythiazole-2(3H)-thiones 2 and 3 were determined by variable-temperature 1H (600 MHz) and 13C (150 MHz) NMR spectroscopy in the temperature range of T = 135-250 K. The barriers to rotation about N2O bonds in cyclic thiohydroxamic acid O-esters 1, 2, and 3 are explained by a superposition of steric and electronic effects.
Keywords: Barrier to rotation, Dynamic NMR, Pyridinethione, Thiazolethione, Nitrogen-Oxygen bond