- Rate constant measurements for the overall reaction of OH + 1-butanol → products from 900 to 1200 K
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The rate constant for the overall reaction OH + 1-butanol → products was determined in the temperature range 900 to 1200 K from measurements of OH concentration time histories in reflected shock wave experiments of tert-butyl hydroperoxide (TBHP) as a fast source of OH radicals with 1-butanol in excess. Narrow-linewidth laser absorption was employed for the quantitative OH concentration measurement. A detailed kinetic mechanism was constructed that includes updated rate constants for 1-butanol and TBHP kinetics that influence the near-first-order OH concentration decay under the present experimental conditions, and this mechanism was used to facilitate the rate constant determination. The current work improves upon previous experimental studies of the title rate constant by utilizing a rigorously generated kinetic model to describe secondary reactions. Additionally, the current work extends the temperature range of experimental data in the literature for the title reaction under combustion-relevant conditions, presenting the first measurements from 900 to 1000 K. Over the entire temperature range studied, the overall rate constant can be expressed in Arrhenius form as 3.24 × 10-10 exp(-2505/T [K]) cm3 molecule-1 s-1. The influence of secondary reactions on the overall OH decay rate is discussed, and a detailed uncertainty analysis is performed yielding an overall uncertainty in the measured rate constant of ±20% at 1197 K and ±23% at 925 K. The results are compared with previous experimental and theoretical studies on the rate constant for the title reaction and reasonable agreement is found when the earlier experimental data were reinterpreted.
- Pang, Genny A.,Hanson, Ronald K.,Golden, David M.,Bowman, Craig T.
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experimental part
p. 2475 - 2483
(2012/05/19)
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- The rotationally resolved electronic spectra of several conformers of 1-hexoxy and 1-heptoxy
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Laser-induced fluorescence excitation spectra of five vibronic bands of 1-hexoxy and three bands of 1-heptoxy have been recorded in a jet-cooled environment. Experimental values of rotational constants for both the X and B states and components of the spin-rotational tensor for the X state were obtained by an analysis of the partially resolved rotational structure of the vibronic bands. Comparing these experimental results with quantum chemistry calculations, and using corresponding assignments of smaller alkoxy radicals as a guide, permitted unambiguous conformational assignments for the bands. The extension of similar assignments to larger alkoxy radicals is also discussed.
- Zu, Lily,Liu, Jinjun,Gopalakrishnan, Sandhya,Miller, Terry A.
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p. 854 - 866
(2007/10/03)
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- Dispersed fluorescence spectroscopy of primary and secondary alkoxy radicals
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Dispersed fluorescence (DF) spectra of 1-propoxy, 1-butoxy, 2-propoxy, and 2-butoxy radicals have been observed under supersonic jet cooling conditions by pumping different vibronic bands of the B-X laser induced fluorescence excitation spectrum. The DF spectra were recorded for both conformers of 1-propoxy, three conformers of the possible five of 1-butoxy, the one possible conformer of 2-propoxy, and two conformers of the possible three of 2-butoxy. Analysis of the spectra yields the energy separations of the vibrationless levels of the ground X and low-lying A electronic state as well as their vibrational frequencies. In all cases, the vibrational structure of the DF spectra is dominated by a CO stretch progression yielding the vco stretching frequency for the X state and in most cases for the A state. In addition to the experimental work, quantum chemical calculations were carried out to aid the assignment of the vibrational levels of the X state and for some conformers the A state as well. Geometry optimizations of the different conformers of the isomers were performed and their energy differences in the ground states were determined. The results of the calculation of the energy separations of the close-lying X and A states of the different conformations are provided for comparison with the experimental observations.
- Jin, Jin,Sioutis, Ilias,Tarczay, Gyoergy,Gopalakrishnan, Sandhya,Bezant, Andrew,Miller, Terry A.
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p. 11780 - 11797
(2008/01/27)
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- Direct investigations of reactions of 1-butoxy and 1-pentoxy radicals using laser pulse initiated oxidation: Reaction with O2 and isomerisation at 293 K and 50 mbar
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The reactions of 1-butoxy and 1-pentoxy radicals were studied using time-resolved and simultaneous measurement of NO2 and OH concentrations in laser pulse initiated oxidation studies followed by numerical simulations of the concentration profiles. The alkoxy radicals were produced selectively by the excimer-laser photolysis of 1-butyl bromide and 1-pentyl bromide at 248 nm and subsequent reaction of the 1-alkyl radicals with O2 and NO. Whereas NO2 was detected by cw-LIF, OH was monitored by laser long-path absorption at 308 nm. All experiments were performed at 293 ± 3 K and a total pressure of 50 mbar. The reactions with O2 and the isomerisations via a 1,5-H-shift, viz., CH3CH2CH2CH2O + O2 → CH3CH2CH2CHO + HO2 (5) CH3CH2CH2CH2O → CH2CH2CH2CH2OH (6) CH3CH2CH2CH2CH2O + O2 → CH3CH2CH2CH2CHO + HO2 (25) CH3CH2CH2CH2CH2O → CH3CHCH2CH2CHOH (26) were investigated. Their rate coefficients were varied, utilizing the FACSIMILE integrator, until the best fits were obtained. Whereas in the case of 1- butoxy radicals absolute rate coefficients k(5) = (1.4 + 0.7) x 10-14 cm3 molecule-1 s-1 and k6 = (3.5 ± 2) x 104 S-1 could be derived, only limiting values for the 1-pentoxy radical reactions k25 ≤ 1 X 10- 13 cm3 molecule-1 s-1 and k26 ≥ 1.0 X 105 S-1 were obtained.
- Hein,Hoffmann,Zellner
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p. 3743 - 3752
(2007/10/03)
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- Absolute Rate Constants for the Addition of Hydroxymethyl Radicals to Alkenes in Methanol Solution
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Absolute rate constants and their temperature dependencies were determined for the addition of hydroxymethyl radicals (.CH2OH) to 20 mono- or 1,1-disubstituted alkenes (CH2 = CXY) in methanol by time-resolved electron spin resonance spectroscopy.With the alkene substituents the rate constants at 298 K (k298) vary from 180 M-1s-1 (ethyl vinylether) to 2.1*106 M-1s-1 (acrolein).The frequency factors obey log A/M-1s-1 = 8.1 +/- 0.1, whereas the activation energies (Ea) range from 11.6 kJ/mol (methacrylonitrile) to 35.7 kJ/mol (ethyl vinylether).As shown by good correlations with the alkene electron affinities (EA), log k298/M-1s-1 = 5.57 + 1.53 * EA/eV (R2 = 0.820) and Ea = 15.86 - 7.38 * EA/eV (R2 = 0.773), hydroxymethyl is a nucleophilic radical, and its addition rates are strongly influenced by polar effects.No apparent correlation was found between Ea or log k298 with the overall reaction enthalpy.
- Wu, J. Q.,Fischer, H.
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p. 167 - 180
(2007/10/02)
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- Disproportionation to Combination Ratios of Alkoxy Radicals with Nitric Oxide
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The disproportionation to combination ratios were measured at 175 deg C for the reactions RO + 15NO -> RO15NO (2a) and RO + 15NO -> RCHO + H15NO (2b), with the following alkoxy radicals: C2H5O, n-C3H7O, n-C4H9O, and i-C4H9O.The alkoxy radical was generated by the termal decomposition of the corresponding alkyl nitrite in the presence of 15NO.The rate of the corresponding isotopically enriched alkyl nitrite was measured by mass spectrometry while the aldehyde rate was determined by gas chromatography.The results obtained for k2b/k2 were 0.22 +/= 0.02, 0.26 +/= 0.03, 0.29 +/= 005, and 033 +/= 0.03, respectively, for C2H5O, n-C3H7O, n-C4H9O, and i-C4H9O.With these values of k2b/k2 we were able to determine the primary quantum yield of the photolysis of the corresponding alkyl nitrites at 366 nm to be, respectively, 0.32 +/= 0.04, 0.44 +/= 0.06, 0.19 +/= 0.04, and 0.19 +/= 0.02.
- Morabito, Paul,Heicklen, Julian
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p. 2914 - 2916
(2007/10/02)
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- Electron Spin Resonance Studies. Part 63. Selective Radical Oxidation by Titanium(IV) Complexes
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Evidence is presented that, when complexed with edta in acid solution, titanium(IV) is an effective oxidant for radicals in which tervalent carbon is bonded to a substituent of +M type.A lower limit for k(TiIV-edta + CHMeOH) is estimated as ca. 108 dm3 mol-1 s-1.When the organic radicals are generated from the TiIII-RO2H couple (R = H or alkyl), a chain reaction operates; but stoicheiometric studies show that the chains are relatively short.
- Gilbert, Bruce C.,Norman, Richard O. C.,Williams Peter S.,Winter, Jeremy N.
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p. 1439 - 1446
(2007/10/02)
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