The yield and extinction coefficient of the solvated electron in methanol: pulse radiolysis of nitrobenzene and tetranitromethane solutions

Abstract

The radical anion [Formula: see text] NB−, which has a strong absorption spectrum from 250–500 nm, is formed by reaction of nitrobenzene with solvated electrons, es−, and hydroxymethyl radical anions, •CO2O−, with k1 = (1.92 ± 0.35) × 1010 M−1 s−1 and k2 = (1.03 ± 0.02) × 1010 M−1 s−1.[Formula: see text]Gελ is constant for NB− over a wide range of nitrobenzene concentrations in basic solution. By assuming that the yields of scavengeable radicals are the same in neutral and basic solutions we obtain ε(NB−)300 nm = (1.66 ± 0.02) × 104 M−1 cm−1. This value is used to evaluate the yield of es− scavengeable by dilute solutions of solutes as G(es−)esc = 1.20 ± 0.03. Extinction coefficients of es−, hydroxymethyl radicals, •CH2OH, and •CO2O− and the oscillator strength of the es− absorption are calculated.The yields of es− determined by previous workers are discussed in terms of dry, damp, geminate, free, spur, and escaped electrons. A model is constructed in terms of damp, spur, and escaped electrons which compares favourably with experimental scavenging results and direct measurements by optical pulse radiolysis.