The Radiation Chemistry of Organic Amides. II. Electron Scavenging Yields in N-Methylpyrrolidinone

The scavenging of e^-_s in N-methylpyrrolidinone(NMP) has been studied using methyl bromide, trans-stilbene and biphenyl as solutes. The rate constants for reaction of e^-_s with these solutes at room temperature (20 ± 2 ^circC) are (1.83 ± 0.11) x 10¹⁰, (2.40 ± 0.2) x 10¹⁰ and (2.09 ± 0.03) x 10¹⁰ dm^3 mol^-1 s^-1, respectively. Yields of methane obtained from γ-irradiated solutions of methyl bromide increased from G(CH_4) = 130 nmol J^-1 for [CH_3Br] = 1.6 x 10^-4 mol dm^-3 to G(CH_4) ≈ 400 nmol J^-1 for [CH_3Br] = 0.56 mol dm^-3. Treatment of the data by the Warman-Asmus-Schuler equation indicated that the yield of e^-_s escaping the spurs, G(e^-_s) is 102 ± 8 nmol J^-1 and that the total ionization yield, G(e^-)_tot is 432 ± 30 nmol J^-1. Yields of stilbene (St^-.) anion observed on pulse radiolysis of trans-stilbene (t-St) solutions give G(e^-_s)_esc = 87 ± 5 nmol J^-1 in fair agreement with the value estimated from the CH_3Br data. Except at the highest [t-St] the yields of St^-. were independent of the pulse length in the range 10-200 ns, but the yield of St^-. approximately doubled as [t-St] increased from 10^-4 to 0.5 mol dm^-3. The yields of biphenyl anion measured at the end of 25 ns pulses followed the same pattern as the St^-. yields, but the increase was only about 55% over a similar concentration range.