A simple method for quantitative estimation of C-H bond lengths in hydrocarbon radical cations

A quantitative correlation between deviations of the C-H bond lengths of hydrocarbon molecules during their adiabatic single ionization and isotropic hyperfine coupling constants with protons of their primary radical cations (RC) was established. A simple method for estimation of the C-H bond lengths of hydrocarbon RC was proposed on the basis of the correlation found. Specific features of the structure of the RC of methane and severaln-alkanes of the general formula [H^*(CH_2nH^*]⁺,n = 0 to 12, were analyzed. A widely used empirical rule, according to which deprotonation of hydrocarbon RC during the ion-molecular process is determined by the proton possessing the highest spin density, was refined and geometrically substantiated.