Radical electrophilicities in solvent

An electrophilicity scale for radicals in solution is reported using the electrophilicity index, an important quantity in conceptual density functional theory. Five different solvents were chosen, for which the static dielectric constant covers the entire range of nonpolar to polar solvents: n-hexane (er = 1.8819), dichloromethane (er = 8.9300), 2-propanol (er = 19.2640), acetonitrile (er = 35.6880) and water (er = 78.3553). The calculations in solution were carried out within the polarizable continuum model through the Integral Equation Formalism (IEFPCM) approach. For water, also conductor-like screening model (COSMO) calculations are reported. The electronic chemical potential remains almost constant when going from gas phase to solution. However, large decreases in chemical hardness can be observed, resulting in more electrophilic radicals compared to the gas phase, and even influencing the overall order of the previously established gas-phase scale. Both solvation models (COSMO and IEF-PCM) lead to essentially the same results.