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The Shielding of H-\alpha in the Stabilized Rotameric Forms of \alpha,\alpha-Di-tert-butylthioacetic Esters. The Electric and Magnetic Anisotropic Effects of the Thione Group

Balasubrahmanyam, SN and Bharathi, Narasimha S and Usha, G (1983) The Shielding of H-\alpha in the Stabilized Rotameric Forms of \alpha,\alpha-Di-tert-butylthioacetic Esters. The Electric and Magnetic Anisotropic Effects of the Thione Group. In: Organic Magnetic Resonance, 21 (8). pp. 474-481.

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Abstract

The currently accepted geometry of carbonyl magnetic anisotropic effects, if regarded as extendable to the thione group, imply that the more deshielded of the two H-\alpha lines in the 'HNMR spectra of \alpha,\alpha-di-tertbutylthioacetic esters should be assigned to the $'180^o$ form' in which C=S is antipenplanar to C-\alpha-H. CNDO results, however, indicate the opposite; the line should be assigned to the $'0^o$ form,' in which C=S eclipses C-\alpha-H, if the predicted considerable increase in Is density at H-\alpha on going from the $'0^o$ form to the $180^o$ form is taken into account. A change in 1s density at H-\alpha as a result of increased branching of dkylation at C-\alpha is also found. These specific effects must be taken into account when discussing the anisotropic effects of C=O or C=S on H-\alpha shifts.

Item Type: Journal Article
Additional Information: The copyright of this article belongs to John Wiley & Sons.
Department/Centre: Division of Chemical Sciences > Organic Chemistry
Date Deposited: 21 Jul 2008
Last Modified: 19 Sep 2010 04:47
URI: http://eprints.iisc.ernet.in/id/eprint/15136

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