Cycloalkylmethyl radicals. 6. The unexpectedly high barrier to the rotation of axial CH2.cntdot. groups in cyclohexylmethyl radicals

Axial and Equatorial Cyclohexylacyl and Tetrahydropyranyl-2-acyl Radicals. An Experimental and Theoretical Study

Axial and equatorial cyclohexylacyl and tetrahydropyranyl-2-acyl radicals gave distinct EPR spectra thanks to surprisingly large beta-hydrogen atom hyperfine splittings that enabled them to be characterized and monitored. DFT computations indicated that the axial species (X = CH(2)) had a higher barrier to rotation about the (O)C(alpha)-C(beta) bond. The computed difference Delta H degrees for the axial and equatorial radicals (R = H, X = CH(2)) was 0.8 kcal mol(-)(1).