Rate Constant and Activation Energy Measurement for the Reaction of Atomic Hydrogen with Methanol, Iodomethane, Iodoethane, and 1-Iodopropane in Aqueous Solution

The Arrhenius parameters for the reaction of hydrogen atoms with methanol in aqueous solution have been determined by use of pulse radiolysis and electron paramagnetic resonance free induction decay attenuation measurements. At 25.5[degrees]C, an absolute scavenging rate constant of (2.84 [+-] 0.07) [times] 10[sup 6] dm[sup 3] mol[sup [minus]1] s[sup [minus]1] has been measured and over the temperature range 10.2-86.4[degrees]C, an activation energy of 29.4 [+-] 0.8 kJ mol[sup [minus]1] has been determined. These values have been used to make minor corrections to rate constant and activation energy values for the reaction of aqueous hydrogen atoms with indomethane, iodoethane, and 1-iodopropane. For these three compounds at 24.3[degree]C, rate constants of (1.17 [+-] 0.07) [times] 10[sup 10], (1.39 [+-] 0.05) [times] 10[sup 10], and (1.42 [+-] 0.06) [times] 10[sup 10] dm[sup 3] mol[sup [minus]1] s[sup [minus]1] and corresponding activation energies of 10.4 [+-] 0.4, 11.8 [+-] 0.4, and 11.9 [+-] 0.4 kJ mol[sup [minus]1] have been respectively calculated over the temperature range 9-52[degrees]C. 44 refs., 5 figs., 1 tab.