13444-87-6Relevant articles and documents
Temperature-dependent rate coefficients for the reactions of Br(2P3/2), Cl(2P3/2), and O(3PJ) with BrONO2
Soller,Nicovich,Wine
, p. 1416 - 1422 (2007/10/03)
A laser flash photolysis-resonance fluorescence technique has been employed to investigate the kinetics of reactions of the important stratospheric species bromine nitrate (BrONO2) with ground-state atomic bromine (k1), chlorine (k2), and oxygen (k3) as a function of temperature (224-352 K) and pressure (16-250 Torr of N2). The rate coefficients for all three reactions are found to be independent of pressure and to increase with decreasing temperature. The following Arrhenius expressions adequately describe the observed temperature dependencies (units are 10-11 cm3molecule-1s-1): k1 = 1.78 exp(365/T), k2 = 6.28 exp(215/T), and k3 = 1.91 exp(215/T). The accuracy of reported rate coefficients is estimated to be 15-25% depending on the magnitude of the rate coefficient and on the temperature. Reaction with atomic oxygen is an important stratospheric loss process for bromine nitrate at altitudes above approximately 25 km; this reaction should be included in models of stratospheric chemistry if bromine partitioning is to be correctly simulated in the 25-35 km altitude regime.
The Synthesis of 15N- and 18O-Isotopically-Enriched Nitryl Bromide, IR Matrix Spectra, and Force Fields of BrNO2, cis-BrONO, and trans-BrONO
Scheffler, Dieter,Willner, Helge
, p. 4500 - 4506 (2008/10/08)
The gas phase reaction between BrNO and O3 at low pressure (2 in about 60% yield. In this manner 15N- and 18O-labeled BrNO2 are prepared. In addition, it is shown that BrNO2 also forms by the heterogeneous low-temperature reaction between gaseous BrNO and solid sulfuric acid, doped with H2O2. It can be assumed that BrNO2 may be formed in a similar way under stratospheric conditions. The isotope scrambling in the reaction between BrNO and 18O3 as well as in the gas phase equilibrium BrNO + NO2 ? BrNO2 + NO are investigated. For the equilibrium constant a lower limit of K298 ≥ 1 × 10-3 is deduced from infrared measurements. A detailed IR and Raman study on BrNO2 is performed. Photolysis of matrix-isolated BrNO2 at different wavelengths leads to a mixture of cis- and trans-BrONO. The vibrational data of BrNO2 (6 fundamentals, 7 combinations), cis-BrONO (5 fundamentals, 1 overtone), and trans-BrONO (4 fundamentals, 8 combinations) as well as the calculated force fields are in excellent agreement with the ab initio values, predicted by T. J. Lee (J. Phys. Chem. 1996, 100, 19847).
Kinetics of the gas-phase reaction of BrNO2 with NO
Bro?ske,Zabel
, p. 8626 - 8631 (2007/10/03)
BrNO2 was prepared in situ in a static reactor (v = 420 L) by photolyzing Br2/NO2/N2 mixtures in the wavelength range 500-700 nm at temperatures between 263 and 294 K. After the lights were switched off, the excess NO was added, and IR and UV spectra were monitored simultaneously as a function of time. From the pseudo-first-order decay of the IR absorption of BrNO2 in the presence of a large excess of NO, the second-order rate constant for reaction 4, BrNO2 + NO → BrNO + NO2, was determined to be k4 = 2.3 × 10-12 exp[(-17.8 ± 2.1) kJ mol-1/RT] cm3molecule-1s-1 (2σ). The measured yields of BrNO were close to 100percent (98 ± 5percent). These results suggest that reaction 4 is unimportant as a loss process of BrNO2 under most tropospheric conditions. Additional experiments on the thermal stability of BrNO2 led to an upper limit of 4.0 × 10-4 s-1 for its thermal gas-phase decomposition rate constant at 298 K in 1 atm of synthetic air. Finally, the mechanism of the Br + NO2 reaction and the thermochemistry of BrNO2 and BrONO are discussed in light of the results of the present experiments and of previous work from the literature.
Ion-Molecule Reactions of Vibrationally State-Selected NO+ with Small Alkyl Halides
Wyttenbach, Thomas,Bowers, Michael T.
, p. 8920 - 8929 (2007/10/02)
The effects of vibrational excitation in NO+ (v=0-5) on its reactivity with small alkyl halides (CnH2n+1X; n=1-3; X=Cl, Br, I) have been investigated under thermal translational conditions.The method combines resonance enhanced multiphoton ionization to form state-selected NO+(v), and Fourier transform in cyclotron resonance techniques to trap, react, and detect ions.Besides vibrational quenching of NO+(v > 0), which is found to be very efficient with alkyl halides, three reaction channels are observed: charge transfer, halide transfer, and CnH2nNO+ formation.Branching ratios and rate constants have been determined for the different channels as a function of the NO+(v=0) vibrationally energy.Endoergic charge transfer is efficiently driven by vibrational excitation.Halide transfer is the major channel if it is significantly exothermic for NO+(v=0).If this is not the case, adding vibrational energy in NO+(v=0) is only marginally effective in driving this channel.The data suggest that rearrangements in NO+-alkyl halide reaction intermediates and in carbonium ions are very rapid.The CnH2nNO+ formation channel is only observed with n-propyl and isopropyl chloride where it is dominant for NO+(v=0).Increasing vibrational excitation inhibits C3H6NO+ formation.The results are discussed in terms of possible reaction mechanisms.
