Reduction potentials of para‐substituted nitrobenzenes—an infrared, nuclear magnetic resonance, and density functional theory study

Abstract

Formal reduction potentials, E°′, of a series of 12 para‐substituted nitrobenzenes (R―C6H4―NO2, where R═NH(CH3), NH2, OCH3, CH3, H, OCO(CH3), Cl, CF3, CO(CH3), CO(H), CN, and NO2) were measured and related to experimental parameters and the calculated descriptors: the lowest unoccupied molecular orbital (LUMO) energy (ELUMO), electron affinity (EA), electrophilicity index (ω), and relative group electronegativity (χR). Excellent correlation was obtained in the linear relationship between E°′ and both ELUMO (R2 > 0.99) and ω, followed by EA, χR, experimental δ1H nuclear magnetic resonance (NMR), infrared asymmetric NO2 stretching frequency (νas), and lastly, δ13C NMR. Calculated ELUMO was found to provide the most convenient theoretical means for predicting experimental E°′ while, together with ω, also giving the highest degree of accuracy. Copyright © 2011 John Wiley & Sons, Ltd.