Reaction rate of H atoms with N2O in hot water

The rate constant of H
- atoms with N2O in water has been measured by a competition method up to 300 °C. Radiolysis with 2.5 MeV electrons generated H
- atoms, and the HD product from their reaction with deuterated tetrahydrofuran (THF-d8) was measured with mass spectroscopy. The concentration of THF-d8 was changed by an order of magnitude in the presence of 25 mM N2O to obtain the ratio of rate constants. To determine the rate constant of H
- with THF-d8, a similar competition vs. 0.2 mM OH- ion was also measured. The reaction rate of H
- with OH- has been accurately determined vs. temperature in previous work, allowing the two unknown rate constants to be deduced. Rate constant of H
- with THF-d8 follows the Arrhenius law ln(k/M−1s−1)=27.33 - (32.30 kJ/mol)/RT. Rate constant of H
- with N2O follows the Arrhenius law ln(k/M−1s−1)=24.50 - (30.42 kJ/mol)/RT. In all likelihood, the N2O reaction proceeds via cis-HNNO
- radical intermediate as in the gas phase, but with participation of a bridging water molecule in the 1,3 hydrogen shift to form N2 and
- OH products.