19876-40-5Relevant articles and documents
Cycloalkylmethyl Radicals. Part 4. Electron Spin Resonance Study of Conformational Equilibria in Cyclohexenylmethyl and 4-Alkylcyclohexenylmethyl Radicals
Walton, John C.
, p. 1641 - 1646 (1986)
For cyclohex-2-enylmethyl and 4-alkoxycyclohex-2-enylmethyl radicals the quasi-axial and the quasi-equatorial conformers can both be observed by e.s.r. spectroscopy.Similary, the axial and equatorial conformers of cyclohex-3-enylmethyl radical can be distinguished by e.s.r. spectroscopy.The conformational free-energy difference of the CH2. group in the 2-position, -ΔGdeg300, was found to be 0.17 +/- 0.03 kcal mol-1 and in the 3-position -ΔGdeg300=0.0 +/- 0.1 kcal mol-1.The Arrhenius parameters for inversion of the half-chair conformation of cyclohex-2-enylmethyl radical were determined by lineshape analysis of the exchange-broadened spectra and found to be: log(kf/s-1)=12.3 - (5.7 kcal mol-1)/2.3RT and log(kb/s-1)=12.0 - (5.5 kcal mol-1)/2.3RT.The barrier to rotation about the C.α-Cβ bond in a cyclohexenylmethyl radicals is much less than the barrier in a cyclohexylmethyl radical because the former radical has only one syn-axial hydrogen on C(5) to impede the rotation whereas the latter radical has two syn-axial hydrogens on C(3) and C(5).
