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 λ_max 270 nm and extinction coefficients of (2.8–3.0)× 10³ dm³ mol^–1 cm^–1.