- Slow chain reactions of Br2 and Cl2 with HI: Multiple state analysis and vibrational relaxation of HBr(v = 2) and HCl(v = 1 - 4)
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Two chain reactions of the general form are studied by realtime detection of infrared chemiluminescence from the vibrationally excited HX(v) products.Both are characterized by k2 a flow cell apparatus at 295 K.Observations are made on Δv = -1 fluorescence from individual vibrational levels, and the results are treated with a complete mathematical analysis for the production of multiple vibrational states and their subsequent individual decays.Effects of vibrational cascading on the measurements of k2 are discussed.The chain propagation rate coefficients determined by this technique for k1(X = Br, Cl) and k2(X = Br, Cl) are 8.9(+/- 1.3) * 10-12, 1.4(+/- 0.3) * 10-10, 3.4(+/- 0.8) * 10-13, and 8.5(+/- 1.1) * 10-17 cm3 molecule-1 s-1, respectively.The deactivation rate coefficients for HBr(v = 2) and HCl(v = 1,2,3,4) by HI are 1.7(+/- 0.2) * 10-12, 1.43 (+/- 0.05) * 10-13, 6.3(+/- 0.5) * 10-13, 7.0(+/- 2.4) * 10-13, and 3.2(+/- 0.7 * 10-12 cm3 molecule-1 s-1, respectively.Vibrational deactivation rate cofficients for HCl(v = 1,2,3,4) by Cl2 are 5.2(+/- 0.3) * 10-15, 2.2(+/- 0.3) * 10-14, 4.3(+/- 4.2) * 10-14, and 2.8(+/- 1.5) * 10-13 cm3 molecule-1 s-1, respectively.The vibrational deactivation efficients of HCl(v = 1 - 4) by HI and Cl2 scale approximately as vn, where n = 2.1(+/- 0.2) and 2.8(+/- 0.2), respectively.
- Dolson, David A.,Leone, Stephen R.
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- Heterogeneous reaction of HOI with sodium halide salts
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The interaction of gaseous HOI with crystalline grains of NaCl and sea-salt and thin films of NaBr crystals has been studied in a wall coated tubular flow reactor coupled to a quadrupole mass spectrometer over a concentration range (0.2-8) × 1012 molecules cm-3 at 278 and 298 K. On a fresh surface, the uptake coefficients determined were independent of temperature with γ = 0.034 ± 0.009, γ = 0.016 ± 0.004, and γ = 0.061 ± 0.021 for NaBr, NaCl, and sea-salt, respectively. No increase in reactivity was observed on addition of water vapor between 0 and 23% relative humidity at 278 K. It was also shown that the reactivity of the salt surface decreased with time of exposure to HOI and that steady-state uptake was slower on aged salt surfaces. Products of the reactions released into the gas phase were IBr, ICl, and IBr + ICl for the reaction of HOI on NaBr, NaCl, and sea-salt surfaces, respectively. The atmospheric implications of the results obtained are briefly discussed.
- Moessinger, Juliane C.,Cox, R. Anthony
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p. 5165 - 5177
(2007/10/03)
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- Kinetics and products of the IO + BrO reaction
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The kinetics and products of the IO + BrO reaction were discussed. The reaction was studied using the technique of laser flash photolysis with kinetic ultraviolet (UV) absorption spectroscopy. No direct measurement of I or Br was performed. IBr was observed as a minor product (klb/kl ld/kl 0.15). The results were compared with previous studies of the IO + BrO reaction, and the atmospheric implications were briefly discussed.
- Rowley, David M.,Bloss, William J.,Cox, R. Anthony,Jones, Roderic L.
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p. 7855 - 7864
(2007/10/03)
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- Characterisation of the tetrahalophosphonium cations PBrnI4 - n+ (0 ≤ n ≤ 4) by 31P MAS NMR, IR and Raman spectroscopy and the crystal structures of PI4+AlCl4-, PI4+AlBr4- and PI4+GaI4-
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The novel tetrahalophosphonium salts PBr4+AsF6-, PI4+AlCl4- and PI4+EBr4- (E = Al, Ga) have been synthesised. A variety of solid complexes containing PBr4+ (e.g. PBr4+AsF6-, PBr4+AlBr4- PBr4+GaBr4-), PI4+ (e.g. PI4+AlCl4-, PI4+AlBr4-, PI4+GaBr4-) or the mixed species PBrnI4 - n+ (0 ≤ n ≤ 4, containing AlBr4-, GaBr4-, AsF6- or SbF6-) have been studied by solid-state 31P MAS NMR and vibrational spectroscopy. The influence of the counter-ion on the chemical shift and the vibrational frequencies are discussed. The crystal structures of PI4+AlCl4-, PI4+AlBr4- and PI4+GaI4- are reported. Evidence for the existence of the hitherto unknown mixed bromoiodophosphonium cations PBr3I+, PBr2I2+ and PBrI3+ has been confirmed by spin-orbit corrected density functional calculations of isotropic 31P chemical shifts for PBrnI4 - n+.
- Aubauer,Kaupp,Klapoetke,Noeth,Piotrowski,Schnick,Senker,Suter
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p. 1880 - 1889
(2007/10/03)
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- Kinetics of the IO radical. 2. Reaction of IO with BrO
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The rate coefficient for the IO + BrO → products (1) reaction was measured using pulsed laser photolysis with a discharge flow tube for radical production and pulsed laser-induced fluorescence and UV absorption for detection of IO and BrO radicals, respectively. Reaction 1 was studied under pseudo-first-order conditions in IO with an excess of BrO between 204 and 388 K at total pressures of 6-15 Torr. The Arrhenius expression obtained for non-iodine atom producing channels is k1a(T) = (2.5 ± 1.0) × 10-11 exp[(260 ± 100)/T] cm3 molecule-1 s-1 independent of pressure. The rate coefficient for the reaction BrO + BrO → products (2) and the UV absorption cross sections of BrO as a function of temperature were also determined as part of this study. The implications of these results to the loss rate of stratospheric ozone are discussed.
- Gilles, Mary K.,Turnipseed, Andrew A.,Burkholder, James B.,Ravishankara,Solomon, Susan
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p. 5526 - 5534
(2007/10/03)
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- The reactions of positive and negative halogen ions with Cl2 and Br2
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A selected ion flow tube study has been carried out at 300 K of the reactions of some atomic and molecular positive and negative halogen ions with Cl2 and Br2 from which the rate coefficients k and ion product distributions have been determined.For the energetic F+ ion reactions, dissociative charge transfer is the dominant process, while for the Cl+ ions, only nondissociative charge transfer occurs.For the less energetic Br+ and I+ reactions, dihalogen molecular ions are important products.All these positive ion reactions proceed quite efficiently, i.e., the k are appreciable fractions of kc, their respective collisional rate coefficients, except for the reactions of Cl2 with the lower energy ions of the spin-orbit triplet of I+, i.e., I+(3P1,0), for which k ca. 0.07kc, this being due to the endothermicities of the reactions.The molecular ion Cl2+ undergoes rapid nondissociative charge transfer with Br2, a process which is, of course, endothermic for the reaction of Br2+ with Cl2 and so no reaction is observed.The less-energetic atomic negative ion reactions proceed-via atom exchange-in which the atomic negative ion of the reactant molecular species and a dihalogen molecule are produced.For those reactions that are exothermic, the k are, within error, equal to (2/3)kc, implying that they proceed via complexes which separate statistically back to reactants (1/3) and forward to products (2/3).Both the Br- + Cl2 and Cl- + Br2 reactions are somewhat less efficient (i.e., k c), a result of the slight endothermicities of the reactions.Of the molecular negative ion reactions, electron transfer is the major process in the Cl2- reaction with Br2, whereas the reaction of Br2- with Cl2 proceeds relatively slowly producing the triatomic ion BrCl2-.
- Spanel, P.,Tichy, M.,Smith, D.
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p. 8660 - 8666
(2007/10/02)
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- Rate constants and equilibrium constants for X + CF3I ? CF3 + IX, where X = Br, C1
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Equilibrium constants for X + CF3I ?k(-1)k(1) CF3 + XI, where X = Cl or Br, have been calculated from molecular constants of CF3I, IBr, and IC1 using statistical thermodynamics. The rate constant of the direct reaction for X ≡ Br has been measured by the temperature-jump method. Rate constants of the reverse reactions have been calculated.
- Dymov,Skorobogatov,Khripun
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p. 714 - 719
(2008/10/08)
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- Non-metal redox kinetics: Hypobromite and hypobromous acid reactions with iodide and with sulfite and the hydrolysis of bromosulfate
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The pulsed-accelerated-flow method is used to study the reactions of OBr- with I- and with SO32- (25.0°C, μ = 0.50 M). Pseudo-first-order rate constants for the OBr- with I- reaction are measured in the range 5930-12900 s-1. The even faster reaction between OBr- and SO32- is studied under second-order conditions. The proposed mechanism includes parallel paths with Br+ transfer to the nucleophile (X = I-, SO32-) via solvent-assisted reaction with OBr- as well as diffusion-controlled reactions between H2O + OBr- + X →OBr XBr + 2OH- OBr- + H2O ?k-aka HOBr + OH- HOBr + X →kHOBr XBr + OH- HOBr (pKa = 8.80) and these nucleophiles. The second-order rate constants (M-1 s-1) are as follows: kOBr = 6.8 (±0.4) × 105 and kHOBr = 5.0 (±0-3) × 109 with I-; kOBr = 1.0 (±0.1) × 108 and kHOBr = 5 (±1) × 109 with SO32-. The intermediate IBr(aq) is unstable with respect to hydrolysis, and it readily forms OI-. The BrSO3- that is formed in the OBr- and HOBr reactions with SO32- hydrolyzes with a rate constant kh = 230 (±20) s-1 at 0.0°C to give SO42- and Br-. The relative hydrolysis rate constants (25°C) for the halosulfates are in the order BrSO3- ? ISO3- ? ClSO3- ? FSO3-.
- Troy, Robert C.,Margerum, Dale W.
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p. 3538 - 3543
(2008/10/08)
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- Millimetr wave measurements of the rotational spectra of ClF, BrF, BrCl, ICl, and IBr
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The rotational spectra of all twelve stable isotopic species of ClF, BrF, BrCl, ICl, and IBr were abserved and measured in the millimeter wave region by means of a sensitive microwave spectrometer.Transitions were detected over a wide range of frequencies for molecules in both the ground vibrational state and several excites states.The rotational spectrum of each molecule was split by the nuclear quadrupole interaction.Altogether, 250 new lines were measured.These correspond to 136 purw rotational transitions.Values of the Dunham coefficients Y01, Y11, Y21, Y31, Y02, Y12, and Y03 were obtained from a computer analysis of the measured frequencies.From these coefficients a number of equilibrium constants were derived to significantly greater accuracy than in previous work.In particular, the equilibrium distance, re, was found to two or three more significant figures.
- Willis, Robert E.,Clark, William W.
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p. 4946 - 4950
(2007/10/02)
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