- 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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- 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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- Rate constants for the reactions of C2H5O, i-C3H7O, and n-C3H7O with NO and O2 as a function of temperature
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The rate constants of the reactions of ethoxy, i-propoxy and n-propoxy radicals with O2 and NO was investigated as function temperature. The radicals were generated by laser photolysis from the appropriate alkyl nitrite and characterized by laser-induced fluorescence. For the reactions with O2, the ethoxy radical reacted somewhat slower than recently recommended. The values obtained for i- and n-propoxy had been combined with the measurements from a recent study at lower temperatures, allowing a more reliable determination of the Arrhenius parameters.
- Fittschen,Frenzel,Imrik,Devolder
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p. 860 - 866
(2007/10/03)
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- Temperature-dependent kinetics studies of the reactions of C2H5O2 and n-C3H7O2 radicals with NO
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The rate coefficients for the gas-phase reactions of C2H5O2 and n-C3H7O2 radicals with NO have been measured over the temperature range of (201-403) K using chemical ionization mass spectrometric detection of the peroxy radical. The alkyl peroxy radical. The alkyl peroxy radicals were generated by reacting alkyl radicals with O2, where the alkyl radicals were produced through the pyrolysis of a larger alkyl nitrite. In some cases C2H5 radicals were generated through the dissociation of iodoethane in a low-power radio frequency discharge. The discharge source was also tested for the i-C3H7O2 + NO reaction, yielding k298 K = (9.1 ± 1.5) × 10-12 cm3 molecule-1 s-1, in excellent agreement with our previous determination. The temperature dependent rate coefficients were found to be k(T) = (2.6 ± 0.4) × 10-12 exp{(380 ± 70)/T} cm3 molecule-1 s-1 and k(T) = (2.9 ± 0.5) × 10-12 exp{(350 ± 60)/T} cm3 molecule-1 s-1 for the reactions of C2H5O2 and n-C3H7O2 radicals with NO, respectively. The rate coefficient at 298 K derived from these Arrhenius expressions are k = (9.3 ± 1.6) × 10-12 cm3 molecule-1 for C2H5O2 radicals and k = (9.4 ± 1.6) × 10-12 cm3 molecule-1 s-1 for n-C3H7O2 radicals.
- Eberhard,Howard
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p. 731 - 740
(2007/10/03)
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- Rates and Mechanisms of the Reactions of Ethanol and Propanol with Fluorine and Chlorine Atoms
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The reactions of C2H5OH (1), C2H5OD (2), C2D5OD (3), 1-C3H7OH (4), 2-C3H7OH (5), 2-C3H7OD (6) with F atoms and the reactions of C2H5OH (7), 1-C3H7OH (8), 1-C3H7OD (9), 2-C3H7OD (10) with Cl atoms have been studied in a discharge flow reactor and a Laval nozzle reactor at room temperature and at pressures of a few mbar.Samples of the reaction mixtures were withdrawn continuously by a molecular beam device and analyzed by a mass spectrometer.The rates of the reactions were measured relative to the standard reactions C2H6 + F (0) and C2H6 + Cl (00) yielding k1/k0 = 1.06 , k2/k0 = 1.25, k3/k0 = 1.20, k4/k0 = 1.26, k5/k0 = 1.06, k6/k0 = 1.20, k7/k00 = 2, k9/k00 = 4.For the reactions of F atoms with alcohols the probability of attack at one of the alkyl H atoms was found to be five times less than at the hydroxyl H atom site.For the reaction of Cl atoms with alcohols no abstraction from the OH group was observed, the abstraction from the alkyl groups follows the thermodynamically favoured route by forming mainly secondary radicals. - Keywords: Chemical Kinetics / Elementary Reactions / Isotope Effects / Mass Spectrometry
- Khatoon, T.,Edelbuettel-Einhaus, J.,Hoyermann, K.,Wagner, H. Gg.
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p. 626 - 632
(2007/10/02)
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- Reactions of some Carboxylic Acid Esters with O(3P) Atoms
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The rates of the reactions of methylformate, ethylformate, methylacetate, ethylacetate and propylacetate with oxygen atoms have been measured in a discharge flow system.The measurements were carried out under oxygen atom excess in the temperature range 3003*mol-1*s-1>: - Keywords: Gas phase kinetics / O atom reactions / Carboxylic acid esters / Mass spectrometry / Arrhenius parameters
- Mix, K.-H.,Schliephake, V.,Wagner, H. Gg.
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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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