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Jointly sponsored by the Department of Chemistry and Biochemistry, CIRES, and the Environmental Program Monday, October 22, 2007 4:00 p.m. CIRES Auditorium University of Colorado, Boulder

Water Dependence of the Kinetics of the HO2 + NO Reaction

Ryan Thalman Dept. of Chemistry and Biochemistry


The reaction of HO2 with NO is important in the atmosphere for two reasons. First, the HO2 + NO reaction is the primary source for production of tropospheric ozone. Tropospheric ozone causes problems because it is a good oxidizer and is a principal component of photochemical smog. Second, HO2 and NO can react in the presence of water to form nitric acid. This provides a sink for HO2 radical in the upper troposphere, terminating the production of other radicals from HO2. The reaction rate of the HO2 + NO reaction was measured under pseudo-first order conditions with and with out water vapor using Laser Flash Photolysis/UV time-resolved spectroscopy. The bimolecular rate constant was determined to be 5x10-13 and 8x10-13 cm3 molecule-1 s-1 with and without water present respectively. The atmospheric implications are discussed.

==The Acid Catalyzed Nitration of Methanol: Formation of Methyl Nitrate Carly Robinson Dept. of Chemistry and Biochemistry


The aqueous phase acid catalyzed reaction of methanol (CH3OH) with nitric acid (HNO3) to yield methyl nitrate (CH3ONO2) under atmospheric conditions has been investigated using gas phase infrared spectroscopy. This reaction was examined as a possible pathway for NOx creation and to see if aerosol production could confound use of CH3ONO2 as a tracer of oceanic influence. Reactions were conducted in aqueous sulfuric acid solutions (50.5-63.3 wt%) with [CH3OH] = 0.0005-0.15 M and [HNO3] = 0.02-0.14 M, at 5.0 – 55.4oC. Methyl nitrate production rates increased linearly with CH3OH and HNO3 and exponentially with sulfuric acid weight percent within the regime studied. Rates increased linearly with nitronium ion (NO2+) concentration, implying that reaction involves NO2+ as nitrating agent under these conditions. The activation energies for 52wt% and 63.6wt% are found to be 66.12 kJ/mol and 16.14 kJ/mol respectively. The resulting rate law, and a parameterized rate equation, k2obs = 1.11E-13 exp(0.336*wt%H2SO4) M-1 sec-1, are also presented.

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