Reaction rate of H atoms with N2O in hot water. (June 2017)

• Record Type: Journal Article
• Authors: Sargent, Leanne; Sterniczuk, Marcin; Bartels, David M.
• Is Part Of: Radiation physics and chemistry. Volume 135(2017)
• Page Start: 18
• Page End: 22
• Publication Date: 2017-06
• Subjects: H atoms -- N2O -- Radiolysis -- Water -- Rate constant -- Activation energy; Radiation chemistry -- Periodicals; Radiometry -- Periodicals; Radiation -- Periodicals; Chimie sous rayonnement -- Périodiques; 539.2
• DOI: 10.1016/j.radphyschem.2017.03.009
• Languages: English
• ISSNs: 0969-806X

Abstract

Abstract: The rate constant of H atoms with N2 O 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 N2 O 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 −1 s −1 )=27.33 - (32.30 kJ/mol)/RT. Rate constant of H with N2 O follows the Arrhenius law ln(k/M −1 s −1 )=24.50 - (30.42 kJ/mol)/RT. In all likelihood, the N2 O 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. Highlights: Rate constant for H with N2 O in water follows Arrhenius behavior to at least 350 °C. Room temperature rate is 2×10 5 M −1 s −1 and activation energy is 31 kJ/mole. Reaction probably proceeds through cis -HNNO intermediate as in gas phase.