Temperature Dependence of Hydrogen Atom Reaction with Nitrate and Nitrite Species in Aqueous Solution

Arrhenius parameters for the reaction of hydrogen atoms with NO 3 -, HNO 2, and NO 2 - in aqueous solution have been determined by the use of pulse radiolysis and electron paramagnetic resonance free induction decay attenuation measurements. At 25.0 °C, the calculated rate constants for these compounds are (5.61 ± 0.51) × 10 6, (3.86 ± 0.09) × 10 8, and (1.62 ± 0.05) × 10 9 dm 3 mol -1 s -1 respectively, with corresponding activation energies of 48.7 ± 1.0 (15.2−84.5 °C), 21.54 ± 0.69 (5.9−62.8 °C) and 15.59 ± 0.36 (6.2−86.8 °C) kJ mol -1 . Computer modeling of these systems suggests that ·H atom reaction with either anion directly produces hydroxide anion and the corresponding NO x radical.