Conformational isomers and rotational barriers in the ketyl radicals of thiophen and thienothiophens
- 1 January 1974
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 6,p. 562-567
- https://doi.org/10.1039/p29740000562
Abstract
The conformational isomers of the ketyl radicals (I)–(III) generated from di-2-thienyl ketone, bis-2-thieno[3,2-b] thienyl ketone, and bis-2-thieno[2,3-b]thienyl ketone, have been detected by e.s.r. spectroscopy. The two preferred conformations are cis–trans and trans–trans. Study of the line shape variations with temperature of the e.s.r. spectra allowed the determination of the activation parameters for the rotation of the aromatic rings. The activation energies follow the same order as the electron-delocalizing power of the nuclei, the values being 31·30, 37·95, 35·73, and 26·57 kJ mol–1 for (I), (II), (III) and for benzophenone ketyl, respectively.Keywords
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