Methyl radical addition to nitroalkane aci-anions in aqueous solution: rate constants and optical absorption spectra
Abstract
Absolute rate constants have been measured for the ˙CH3 radical addition to the aci-anions of nitromethane, nitro-ethane, 1-nitropropane, and 2-nitropropane. The respective values of (1.35 ± 0.2)× 108, (1.60 ± 0.3)× 107, (1.35 ± 0.3)× 107, and (2.35 ± 0.5)× 106 dm3 mol–1 s–1 indicate a nucleophilic character of the methyl radical. From Taft's relationship on the inductive substituent effect, ρ*+ 8.9 is derived. The optical absorption spectra of the methyl radical adducts, R1R2CH3NO2·-, are characterized by λmax 270 nm and extinction coefficients of (2.8–3.0)× 103 dm3 mol–1 cm–1.