http://joenschem.com/yahoo_site_admin/assets/docs/atkinson2000r.93190106.pdf

Atmospheric chemistry of VOCs and NOx

Atmospheric degradation of volatile organic compounds

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Gas-phase tropospheric chemistry of biogenic volatile organic compounds: a review

Ozonolysis is a major tropospheric removal mechanism for unsaturated hydrocarbons and proceeds via "Criegee intermediates"--carbonyl oxides--that play a key role in tropospheric oxidation models. However, until recently no gas-phase Criegee intermediate had been observed, and indirect determinations of their reaction kinetics gave derived rate coefficients spanning orders of magnitude. Here, we report direct photoionization mass spectrometric detection of formaldehyde oxide (CH(2)OO) as a product of the reaction of CH(2)I with O(2). This reaction enabled direct laboratory determinations of CH(2)OO kinetics. Upper limits were extracted for reaction rate coefficients with NO and H(2)O. The CH(2)OO reactions with SO(2) and NO(2) proved unexpectedly rapid and imply a substantially greater role of carbonyl oxides in models of tropospheric sulfate and nitrate chemistry than previously assumed.

http://science.sciencemag.org/content/sci/335/6065/204.full.pdf

Direct Kinetic Measurements of Criegee Intermediate (CH2OO) Formed by Reaction of CH2I with O2

A detailed kinetic analysis of the complex reaction systems arising from the ozonolysis of C 2H4 and (CH3)2CdC(CH3)2 (TME), respectively, is carried out, using master equations and statistical rate theory. The thermochemical as well as the molecular data required are obtained from CCSD(T)/TZ2P and B3LYP/ DZP calculations. It is shown that the primary ozonides are not collisionally stabilized under atmospheric conditions. In the reaction sequence for O3 + TME, the same is true for CH2dC(CH3)OOH formed from (CH3)2COO, which completely dissociates to give OH radicals. However, in this system, a pressure dependence is predicted for the relative branching fractions of the reactions of the Criegee intermediate. Under atmospheric conditions, for both examples, the product yields obtained are in reasonable agreement with experimental results.

/pdf/energetics-kinetics-and-product-distributions-of-the-271s6l32ph.pdf

Energetics, Kinetics, and Product Distributions of the Reactions of Ozone with Ethene and 2,3-Dimethyl-2-butene

https://sites.smu.edu/dedman/catco/publications/pdf/ChemPhysLett_252_221_1996.pdf

Formation of OH radicals in the gas phase ozonolysis of alkenes: the unexpected role of carbonyl oxides

Kinetic measurements as well as B3LYP/ and MP2/6-31G(d,p) calculations provide evidence that carbonyl oxides formed in the gas-phase ozonolysis of alkylated alkenes are an important source of OH radicals. In the gas-phase ozonolysis of propene, cis-2-butene, trans-2-butene, tetramethylethene, and isoprene, 18, 17, 24, 36, and 19% OH radicals (relative to reacted ozone, error margin ≤4%) are measured using CO as a scavenger for OH. The quantum chemical calculations show that OH radical production depends on syn positioned methyl (alkyl) groups and their interaction with the terminal O atom of a carbonyl oxide. For example, in the gas-phase ozonolysis of ethene only 5% OH radicals are measured while for a carbonyl oxide with syn-positioned methyl (alkyl) group, a much larger amount of OH radicals is formed. This is due to the fact that 1,4 H migration and the formation of an intermediate hydroperoxy alkene, that is prone to undergo OO bond cleavage, is energetically more favorable than isomerization to diox...

/pdf/kinetic-and-theoretical-investigation-of-the-gas-phase-3zfsmzkuy9.pdf

Kinetic and Theoretical Investigation of the Gas-Phase Ozonolysis of Isoprene: Carbonyl Oxides as an Important Source for OH Radicals in the Atmosphere

The OH radical yields generated in the ozonolysis of ethene (ET), propene (PR), cis-2-butene (CB), trans-2-butene (TB), 2,3-dimethyl-2-butene (TME), and isoprene (ISP) in the presence of 20 Vol.% O2 have been determined in a darkened glass reactor at 1 bar total pressure. The hydroxyl radicals formed were scavenged by an excess of CO added to the systems. The O2 present converted H atoms formed in this reaction into HO2. From measurements of the increase in CO2 generation by FTIR the OH formation yields were determined to be 0.08 (ET), 0.18 (PR), 0.17 (CB), 0.24 (TB), 0.36 (TME), and 0.19 (ISP), respectively, per molecule of reacted ozone. The combined error in the OH determinations is estimated to be <10%. © 1997 John Wiley & Sons, Inc.

Roland Gutbrod

Papers

Energetics, Kinetics, and Product Distributions of the Reactions of Ozone with Ethene and 2,3-Dimethyl-2-butene

Formation of OH radicals in the gas phase ozonolysis of alkenes: the unexpected role of carbonyl oxides

Kinetic and Theoretical Investigation of the Gas-Phase Ozonolysis of Isoprene: Carbonyl Oxides as an Important Source for OH Radicals in the Atmosphere

On the use of CO as scavenger for OH radicals in the ozonolysis of simple alkenes and isoprene