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Equilibrium geometries and isotropic hyperfine coupling constants have been estimated for the series of radicals CHnF3_n, CHnCla-n, CClnFa_n and S1HnF~-n using the INDO method. The theoretical hyperfine splittings agree well with experimental values including the unusually large proton splittings of 34"6 G and 89"9 G recently reported for SiH2F and SiHF~.

The E.S.R. spectra of the fl-fluoroisopropyl radical and the fl-fluoro, fl,fl-difluoro and fl,fl, fl-trifluoroethyl radicals have been recorded in fluid solutions. The conformational preferences and barriers to internal rotation in these species have been determined from an investigation of the temperature dependence of the fi-fluorine and fi-proton hyperfine coupling constants. The experimental hyperfine splittings have been compared with theoretical values calculated by the INDO method.

Mittels ESR‐Spektroskopie wird der Unterschied von 0‐ gegenüber S‐haltigen Radikalen hinsichtlich deren Planarität, Elektronendelokalisierung und Rotationsbarrieren an den Modellverbindungen (I)‐(IV) untersucht.