Pulse radiolysis studies of solutions of tetranitromethane in iso-propanol

Abstract

Tetranitromethane (TNM) reacts by a dissociative electron capture process with solvated electrons in isopropanol (k_{TNM + e^–s}= 2.45 × 10¹⁰ M^–1 s^–1) to produce nitroform anions, C(NO₂)^–₃, and NO₂. Iso-propanol radicals and iso-propanolperoxy radicals also reduce TNM via an electron transfer reaction with bimolecular rate constants of 7 × 10⁹ M^–1 s^–1 and 9 × 10⁸ M^–1 s^–1, respectively. In neutral and acid (HClO₄) solutions C(NO₂)^–₃ ions are neutralized to C(NO₂)₃H by reaction with solvated protons (k= 3.2 × 10⁸ M^–1 s^–1) and by a proton transfer reaction from isopropanol molecules (k= 4.5 × 10² M^–1 s^–1). C(NO₂)₃H dissociates with k= 3.2 × 10³ s^–1. The equilibrium constant of C(NO₂)₃H ⇌ C(NO₂)^–₃+ H⁺_sol in isopropanol was determined to be K= 1.0 × 10^–5 M. The yield of scavengable reducing species in irradiated isopropanol increases from G= 3.5 at 6.3 × 10^–6 M TNM to G= 6.4 at 3.2 × 10^–2 M TNM in argon saturated solutions, and from G= 0.75 to G= 4.2 for the same concentrations of TNM in O₂ saturated solutions. G(free solvated electrons) was measured to be 1.2. The formation and disappearance of ions have been observed directly by means of pulse radiolysis conductivity measurements. The specific equivalent conductance of C(NO₂)^–₃ ions and solvated protons was determined to be Λ_{C(NO2)3^–+ Hsol⁺}= 51 Ω^–1 cm² equiv.^–1.