Radical Polarity

The polarity of a radical intermediate profoundly impacts\nits reactivity\nand selectivity. To quantify this influence and predict its effects,\nthe electrophilicity/nucleophilicity of >500 radicals has been\ncalculated.\nThis database of open-shell species entails frequently encountered\nsynthetic intermediates, including radicals centered at sp<sup>3</sup>, sp<sup>2</sup>, and sp hybridized carbon atoms or various heteroatoms\n(O, N, S, P, B, Si, X). Importantly, these <i>computationally</i> determined polarities have been <i>experimentally</i> validated\nfor electronically diverse sets of >50 C-centered radicals, as\nwell\nas N- and O- centered radicals. High correlations are measured between <i>calculated</i> polarity and <i>quantified</i> reactivity,\nas well as within parallel sets of competition experiments (across\ndifferent radical types and reaction classes). These multipronged\nanalyses show a strong relationship between the computed electrophilicity,\nω, of a radical and its relative reactivity (<i>k</i><sub>rel</sub> vs Δω slopes up to 40; showing mere Δω\nof 0.1 eV affords up to 4-fold rate enhancement). We expect this <i>experimentally validated database</i> will enable reactivity\nand selectivity prediction (by harnessing polarity-matched rate enhancement)\nand assist with troubleshooting in synthetic reaction development.