21255-83-4Relevant articles and documents
A combined matrix isolation and ab initio study of bromine oxides
Galvez, Oscar,Zoermer, Anja,Loewenschuss, Aharon,Grothe, Hinrich
, p. 6472 - 6481 (2008/10/09)
Bromine oxides have been generated by passing a mixture of Br 2/O2/Ar through a microwave discharge. The products were stabilized at 6.5 K in an excess amount of argon. Infrared spectroscopy was used to analyze the species formed; experiments with enriched 18O 2 and ab initio calculations were carried out to assist in the assignment of the spectra. Besides the known species BrO, OBrO, and BrBrO, spectroscopic evidence for BrOBrO, BrBrO2, and a new isomer of Br2O3 is reported for the first time. Extensive comparisons are drawn between the present studies and previous experimental and theoretical works. The chemistry involved in the production of the observed compounds is discussed. The assignments are corroborated by the good correlation between observed and calculated band positions and intensities.
The visible absorption spectrum of OBrO, investigated by fourier transform spectroscopy
Fleischmann, Oliver C.,Meyer-Arnek, Julian,Burrows, John P.,Orphal, Johannes
, p. 5093 - 5103 (2008/10/09)
By the utilization of a new laboratory method to synthesize OBrO employing an electric discharge, the visible absorption spectrum of gaseous OBrO has been investigated. Absorption spectra of OBrO have been recorded at 298 K, using a continuous-scan Fourier transform spectrometer at a spectral resolution of 0.8 cm-1. A detailed vibrational and rotational analysis of the observed transitions has been carried out. The FTS measurements provide experimental evidence that the visible absorption spectrum of OBrO results from the electronic transition C(2A2)-X(2B1). Vibrational constants have been determined for the C(2A 2) state (ω1 = 648.3 ±1.9 cm-1 and ω2 = 212.8 ±1.2 cm-1) and for the X( 2B1) state (ω1 = 804.1 ± 0.8 cm-1 and ω2 = 312.2 ± 0.5 cm-1). The vibrational bands (1,0,0), (2,0,0), and (1,1,0) show rotational structure, whereas the other observed bands are unstructured because of strong predissociation. Rotational constants have been determined experimentally for the upper electronic state C(2A2). By modeling the band contours, predissociation lifetimes have been estimated. Further, an estimate for the absorption cross-section of OBrO has been made by assessing the bromine budget within the gas mixture, and atmospheric lifetimes of OBrO have been calculated using a photochemical model.
Formation of high concentrations of BrO2 in acidic bromate solutions
Alves, Wagner A.,Cortes, Carlos E. S.,Faria, Roberto B.
, p. 4112 - 4114 (2008/10/09)
A new procedure to produce the BrO2 transient species allowed time-resolved UV-vis spectra that show a structured band (λmax = 502 nm) in dichloromethane to be obtained. In water, because of the increase of the dielectric constant, the λmax presents a blue shift to 474 nm and the species decomposes much faster. The time-resolved spectra show evidence for its equilibrium with a nonidentified colorless form. This route opens new possibilities to the study this species in solution.
Low-temperature interaction between hydrogen bromide and ozone
Savilov,Yagodovskaya,Zosimov,Lunin
, p. 930 - 934 (2007/10/03)
The heterogeneous chemical reactions between ozone and HBr and a solution of between ozone and HBr adsorbed on the surface of ice were studied in the temperature range 77-223 K. The reagents interacted instantaneously with the formation of dark brown, golden yellow, and yellow-orange condensates. According to the low-temperature IR spectra, the reaction products were Br2O, Br2O3, BrO2, and Br2O4 bromine oxides. The initial product was Br2O, which afterward underwent successive oxidation. Ab initio quantum-chemical calculations were performed to determine the structures and relative stabilities of the specified bromine oxides.
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.
Fourier transform infrared spectroscopic study of Br2O and OBrO
Chu, Liang T.,Li, Zhuangjie
, p. 68 - 76 (2008/10/08)
Vibrational frequencies of gaseous Br2O and OBrO were observed using the Fourier transform infrared spectrometer. For the first time, bands at 629.0 cm-1 (ν3) and 532.9 cm-1 (ν1) were recorded for both Br-O asymmetric and symmetric stretching vibrations of gaseous Br2O. Two fundamental vibrations were observed at 798.7cm-1(ν1) and 846.3cm-1(ν3) for the O18BrO radical. In addition, two new peaks at 2333 cm-1 and 668 cm-1 were observed in a HOBr spectrum. They are tentatively assigned to the H-Br and Br-O stretching vibrations of a HOBr isomer on the basis of ab initio computational results.
A study of the BrO and BrO2 radicals with vacuum ultraviolet photoelectron spectroscopy
Dyke,Gamblin,Hooper,Lee,Morris,Mok,Chau
, p. 6262 - 6274 (2007/10/03)
The BrO radical, prepared by the Br+O3 reaction, has been investigated by ultraviolet photoelectron spectroscopy. Two vibrationally resolved bands were observed corresponding to the ionizations BrO+(X3Σ-)←BrO(X2Π) and BrO+(a 1Δ)←BrO(X 2Π). These assignments are supported by the results of complete active space self-consistent field/multireference configuration interaction (CASSCF/MRCI) calculations performed as part of this work. The adiabatic ionization energies of these bands were measured as (10.46±0.02) and (11.21±0.02)eV, respectively. Measurement of the vibrational separations in these bands led to estimates of the vibrational constants in the ionic states of (840±30) cm-1 and (880±30) cm-1, and Franck-Condon simulations of the vibrational envelopes gave values of the ionic state bond lengths of (1.635±0.005) and (1.641±0.005) A for the X 3Σ- and a 1Δ states of BrO+, respectively. The O+Br2 reaction was found to give a band at (10.26±0.02) eV associated with a reaction product. Comparison of the results obtained for the Br+O3 reaction showed that it could not be assigned to ionization of BrO. Calculations of the first adiabatic ionization energies and Franck-Condon simulations of the vibrational envelopes of the first photoelectron bands of BrO2 and Br2O and their isomers demonstrated that this band corresponds to the first ionization of OBrO, the BrO+2 (X 1A1)←BrO2(X 2B1) ionization. Franck-Condon simulations were performed with the experimental geometry of BrO2(X 2B1) but with different cationic state geometries. The simulated envelope which most closely matched the experimental envelope gave geometrical parameters of re = 1.6135 A and 〈OBrO= 117.5° for the ionic state.
Laboratory Formation of OBrO and Its Reactivity toward Ozone at 298 K
Li, Zhuangjie
, p. 1206 - 1213 (2007/10/03)
Bromine dioxide, OBrO, has been formed in our laboratory using three methods in a discharge flow reactor: (1) O + Br2; (2) Br + O3; and (3) microwave discharge of a Br2/O2/He mixture. The OBrO radical was detected using a mass spectrometer at m/e = 111/113. A new mechanism is proposed to account for the formation of the OBrO in these methods. The key to this mechanism is the self-reaction of vibrationally excited BrO. At 298 K, ground-state OBrO does not notably react with ozone, and an upper limit rate constant for the reaction of the ground-state OBrO with ozone was estimated to be k13 ≤ 5 × 10-16 cm3 molecule-1 s-1. The vibrationally excited OBrO, on the other hand, is at least 3 orders of magnitude more reactive toward ozone than the ground-state OBrO, with a rate constant of k13a = (5.4 ± 2.7) × 10-13 cm3 molecule-1 s-1.
A kinetic study on reactions of OBrO with NO, OClO, and ClO at 298 K
Li, Zhuangjie,Tao, Zhining
, p. 117 - 123 (2008/10/08)
Kinetics for reactions of OBrO with NO, OClO, and ClO were examined using discharge flow coupled with mass spectrometer (DF/MS) technique at 298 K and total pressure of 1 torr under the pseudo-first-order condition in which OBrO was a minor reactant. The rate constant for the reaction of OBrO with NO was determined to be k2=(1.77±0.32)×10-12 cm3 molecule-1 s-1. NO2 was found to be the product for OBrO+NO. The rate constants for OBrO reactions with OClO and ClO were estimated to be k3-14 and k4-13 cm3 molecule-1 s-1, respectively.
The OBrO C(2A2)←X(2B1) absorption spectrum
Miller, Charles E.,Nickolaisen, Scott L.,Francisco, Joseph S.,Sander, Stanley P.
, p. 2300 - 2307 (2007/10/03)
The highly structured visible absorption spectrum of the bromine dioxide radical, OBrO, has been observed in the 15 500-26 000 cm-1 region. The spectrum is dominated by a long progression in the Br-O symmetric stretching motion (ν′1) and a series of short progressions built on the bending mode (ν′2); there are no features associated with the excitation of the antisymmetric stretching mode (ν′3). The spectrum also contains numerous transitions originating from the (0,1,0) and (1,0,0) vibrational levels of the electronic ground state, X(2B1). A simultaneous fit to all of the observed vibronic features yielded the frequencies ν″1=799.4 cm-1, ν″2=317.5 cm-1, ω′1=641.5 cm-1, ω′2=210.7 cm-1, and a band origin T0=15 863 cm-1. Franck-Condon simulations combined with ab initio calculations of the four lowest OBrO doublet electronic states identify the spectrum as arising from the C(2A2)←X(2B1) electronic transition.
