- Detailed rate coefficients and the enthalpy change of the equilibrium reaction over the temperature range 345-385 K
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The reaction between OH and C6H6 in He has been studied over the pressure range 250-500 Torr and the temperature range 345-385 K by means of the laser-photolysis/laser-induced-fluorescence technique.Analysis of the temporal profile of yielded the detailed rate coefficients and the equilibrium constant for the reaction OH + C6H6 + M HOC6H6 + M.The temperature dependence of the rate coefficients for the forward, the reverse,and the adduct-loss reactions have been determined to be kf = (2.0+/-0.1)x10-14 exp cm3molecule-1 s-1, kr = (3.0+/-0.2)x1012 exp s-1, and ka = (1.7+/-0.3)x106 exp s-1, respectively.The temperature dependence of the equilibrium constant led to the enthalpy of reaction ΔH(365+/-20 K) = -(20.0+/-1.2) kcal mol-1 and the entropy of reaction ΔS(365+/-20 K) = -(33.6+/-2.5 cal K-1 mol-1, greater than previously reported values; after correction for temperature dependence, ΔH0(298 K) = -(19.9+/-1.2) kcal mol-1 and ΔS0(298 K) = -(33.4+/-2.6) cal K-1 mol-1.
- Lin, Shih-Chieh,Kuo, Tsu-Chi,Lee, Yuan-Pern
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- Gas phase oxidation of benzene: Kinetics, thermochemistry and mechanism of initial steps
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Volatile aromatic compounds participate to a significant extent to the pollution of the troposphere and to ozone formation. A new investigation of the primary steps of the benzene oxidation, involving complementary experimental and theoretical approaches,
- Raoult, Severine,Rayez, Marie-Therese,Rayez, Jean-Claude,Lesclaux, Robert
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p. 2245 - 2253
(2007/10/03)
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- Gas-phase reaction of the OH-benzene adduct with O2: Reversibility and secondary formation of HO2
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The reaction of OH radicals with benzene and consecutive reactions of benzene-OH adducts with O2 were studied in the gas phase in N2-O2 mixtures at atmospheric pressure and room temperature. OH was produced by pulsed 248 n
- Bohn, Birger,Zetzsch, Cornelius
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p. 5097 - 5107
(2007/10/03)
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- Evidence for Hydroxyl Radicals as an Active Species Generated from Udenfriend's Reagent
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The inhibitory effect of six aliphatic alcohols, which are typical OH radical scavengers, on the yield of phenol in the oxidations of benzene with Fenton's (Fe(II) + H2O2) and Udenfriend's (Fe(II) + EDTA + O2 + L-ascorbic acid) reagents has been examined.
- Ito, Sotaro,Ueno, Kazuhiko,Mitarai, Akira,Sasaki, Kazuo
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p. 255 - 259
(2007/10/02)
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- OH-Radical-Induced Oxidation of Benzene in the Presence of Oxygen: R.+O2 RO2.. Equilibria in Aqueous Solution. A Pulse Radiolysis Study
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The reaction of hydroxycyclohexadienyl radical with oxygen was studied by pulse radiolysis.At room temperature the establishment of the equilibria between the hydroxycyclohexadienyl radical (1), oxygen and the hydroxycyclohexadienperoxyl radicals 5-hydroxy-1,3-cyclohexadiene-6-peroxyl radical (3) and 6-hydroxy-1,4-cyclohexadiene-4-peroxyl radical (4), was observed.From the kinetic analysis of the decay of radical 1 at 310 nm overall forward and reverse rate constants of k=3.1*108 dm3 mol-1 s-1 and k=1.2*104 s-1 were obtained.From the analysis of the transient spectra and the products of pulse-irradiated solutions it is concluded that in the equilibrium radical 4 is much favoured over radical 3.
- Pan, Xian-Ming,Sonntag, Clemens von
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p. 1337 - 1340
(2007/10/02)
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- Adduct Formation of OH Radicals with Benzene, Toluene, and Phenol and Consecutive Reactions of the Adducts with NOX and O2
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The formation of the adducts of OH with benzene, toluene and phenol and consecutive reactions of the adducts with NO, NO2 and O2 are investigated in the temperature range from ca. 298-374 K employing the flash photolysis/resonance fluorescence technique in Ar at 133 mbar.Biexponential decays of OH can be observed over at least 2 orders of magnitude in the presence of the aromatics, and the three reaction channels: abstraction of H by OH, addition of OH and unimolecular decomposition of the adduct are distinguished in overlapping temperature ranges.Rate constants and preliminary Arrhenius parameters are obtained for these channels for benzene, toluene, and phenol.The reactions of the adducts with NO are very slow and can be neglected (-13 cm3s-1) in all three cases.Values of ca. 3*10-11 cm3s-1 are obtained for the rate constants of the reactions of the adducts with NO2, almost independent of reactant and temperature.Preliminary determinations of the adduct reactivities against O2 ca. 2*10-16 (benzene-OH) and ca. 5*10-16 cm3s-1 (toluene-OH) near room temperature indicate that this path predominates under tropospheric conditions.The results for O2 are confirmed by direct observations of the adduct benzene-OH by the cw UV-laser longpath absorption technique.
- Knispel, Ralf,Koch, Rainald,Siese, Manfred,Zetzsch, Cornelius
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p. 1375 - 1379
(2007/10/02)
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- Direct Detection of Hydroxy-Cyclohexadienyl in the Gas Phase by cw-UV-Laser Absorption
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Formation of hydroxy-cyclohexadienyl (HCHD), the product of the OH + benzene reaction, has been observed directly in the gas phase at 298 K using long-path cw-UV-laser absorption at 308 nm.The absorption cross section at this wavelength is found to be (9.
- Fritz, B.,Handwerk, V.,Preidel, M.,Zellner, R.
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p. 343 - 344
(2007/10/02)
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- REACTIVITY OF SOME CONDENSED AROMATIC HYDROCARBONS DURING RADIATION OXIDATION IN AQUEOUS SOLUTIONS
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The effect of increase in the degree of annellation on the rate of the reaction of OH radicals with the molecules of aromatic compounds was investigated.It was found that during radiation hydroxylation the reaction rate constant increases by three orders
- Vysotskaya, N. A.,Bortun, L. N.,Rekasheva, A. F.
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p. 2275 - 2279
(2007/10/02)
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