Showing papers by "James B. Burkholder published in 2007"
TL;DR: Rate coefficients for the gas-phase reaction of the OH radical with (E)-2-pentenal, (E-2-hexenal and (E -2-heptenal) and a series of unsaturated aldehydes, over the temperature range 244-374 K at pressures between 23 and 150 Torr (He, N(2)) are reported.
Abstract: Rate coefficients for the gas-phase reaction of the OH radical with (E)-2-pentenal (CH3CH2CHCHCHO), (E)-2-hexenal (CH3(CH2)2CHCHCHO), and (E)-2-heptenal (CH3(CH2)3CHCHCHO), a series of unsaturated aldehydes, over the temperature range 244–374 K at pressures between 23 and 150 Torr (He, N2) are reported. Rate coefficients were measured under pseudo-first-order conditions in OH with OH radicals produced via pulsed laser photolysis of HNO3 or H2O2 at 248 nm and detected by pulsed laser-induced fluorescence. The rate coefficients were independent of pressure and the room temperature rate coefficients and Arrhenius expressions obtained are (cm3 molecule−1 s−1 units): k1(297 K)
=
(4.3 ± 0.6)
× 10−11, k1(T)
=
(7.9 ± 1.2)
× 10−12 exp[(510 ± 20)/T]; k2(297 K)
=
(4.4 ± 0.5)
× 10−11, k2(T)
=
(7.5 ± 1.1)
× 10−12 exp[(520 ± 30)/T]; and k3(297 K)
=
(4.4 ± 0.7)
× 10−11, k3(T)
=
(9.7 ± 1.5)
× 10−12 exp[(450 ± 20)/T] for (E)-2-pentenal, (E)-2-hexenal and (E)-2-heptenal, respectively. The quoted uncertainties are 2σ
(95% confidence level) and include estimated systematic errors. Rate coefficients are compared with previously published room temperature values and the discrepancies are discussed. The atmospheric degradation of unsaturated aldehydes is also discussed.
31 citations
TL;DR: The visible absorption spectrum of the acetyl radical, CH(3)CO, was measured between 490 and 660 nm at 298 K using cavity ring-down spectroscopy and agreement of the measured rate coefficients for the reaction of the absorbing species with O(2) and O(3).
Abstract: The visible absorption spectrum of the acetyl radical, CH3CO, was measured between 490 and 660 nm at 298 K using cavity ring-down spectroscopy. Gas-phase CH3CO radicals were produced using several methods including: (1) 248 nm pulsed laser photolysis of acetone (CH3C(O)CH3), methyl ethyl ketone (MEK, CH3C(O)CH2CH3), and biacetyl (CH3C(O)C(O)CH3), (2) Cl + CH3C(O)H → CH3C(O) + HCl with Cl atoms produced via pulsed laser photolysis or in a discharge flow tube, and (3) OH + CH3C(O)H → CH3CO + H2O with two different pulsed laser photolysis sources of OH radicals. The CH3CO absorption spectrum was assigned on the basis of the consistency of the spectra obtained from the different CH3CO sources and agreement of the measured rate coefficients for the reaction of the absorbing species with O2 and O3 with literature values for the CH3CO + O2 + M and CH3CO + O3 reactions. The CH3CO absorption spectrum between 490 and 660 nm has a broad peak centered near 535 nm and shows no discernible structure. The absorption cr...
21 citations
TL;DR: The state of knowledge for the atmospheric processing of pinonaldehyde is reviewed, and its role as a marker for alpha-pinene (monoterpene) chemistry in the atmosphere is discussed.
Abstract: The rate coefficient for the reaction of OH with pinonaldehyde (C10H16O2, 3-acetyl-2,2-dimethyl-cyclobutyl-ethanal), a product of the atmospheric oxidation of α-pinene, was measured under pseudo-fi...
13 citations