Estimation of gas-phase hydroxyl radical rate constants of organic compounds from molecular orbital calculations

The photoelectron spectra of the tautomeric 1,2,3,- and 1,2,4-triazole and 1,2,3,4-tetrazole systems have been compared with the corresponding N-methyl derivatives. The dominant tautomers in the gas phase have been identified as 2 H-1,2,3-triazole, 1 H-1,2,4-triazole and 2H-tetrazole.Full optimisation of the equilibrium geometry by ab initio molecular orbital methods leads to the same conclusions, for relative stability of the tautomers in each of the triazoles, but the calculations wrongly predict the tetrazole tautomerism.

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Molecular orbital structures of sulfones

Canadian Journal of Chemistry ◽

10.1139/v82-108 ◽

1982 ◽

Vol 60 (6) ◽

pp. 730-734 ◽

Cited By ~ 7

Author(s):

Russell J. Boyd ◽

Jeffrey P. Szabo

Keyword(s):

Crystal Structure ◽

Gas Phase ◽

Molecular Orbital ◽

Geometry Optimization ◽

Membered Ring ◽

Molecular Orbital Calculations ◽

Bond Lengths ◽

Comparison With Experiment ◽

The Difference

Abinitio molecular orbital calculations are reported for several cyclic and acyclic sulfones. The geometries of XSO2Y, where X, Y = H, F, or CH3 are optimized at the STO-3G* level. Similar calculations are reported for the smallest cyclic sulfone, thiirane-1,1 -dioxide, as well as the corresponding sulfoxide, thiirane-1-oxide, and the parent sulfide, thiirane. Where comparison with experiment is possible, the agreement is satisfactory. In order to consider the possibility of substantial differences between axial and equatorial S—O bonds in the gas phase, as observed in the crystal structure of 5H,8H-dibenzo[d,f][1,2]-dithiocin-1,1-dioxide, STO-3G* calculations are reported for a six-membered ring, thiane-1,1-dioxide, and a model eight-membered ring. Limited geometry optimization of the axial and equatorial S—O bonds in the chair conformations of the six- and eight-membered rings leads to bond lengths of 1.46 Å with the difference being less than 0.01 Å.

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Prediction of Rate Constants for Gas‐Phase Reactions of Nitrate Radical with Organic Compounds: A New Structure–Activity Relationship

ChemPhysChem ◽

10.1002/cphc.201000673 ◽

2010 ◽

Vol 11 (18) ◽

pp. 3909-3920 ◽

Cited By ~ 38

Author(s):

Jamila Kerdouci ◽

Bénédicte Picquet‐Varrault ◽

Jean‐François Doussin

Keyword(s):

Gas Phase ◽

Organic Compounds ◽

Rate Constants ◽

Structure Activity Relationship ◽

Activity Relationship ◽

Nitrate Radical ◽

Gas Phase Reactions ◽

Structure Activity

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Constraining nucleation, condensation, and chemistry in oxidation flow reactors using size-distribution measurements and aerosol microphysical modelling

10.5194/acp-2018-223 ◽

2018 ◽

Cited By ~ 1

Author(s):

Anna L. Hodshire ◽

Brett B. Palm ◽

M. Lizabeth Alexander ◽

Qijing Bian ◽

Pedro Campuzano-Jost ◽

...

Keyword(s):

Size Distribution ◽

Gas Phase ◽

Organic Compounds ◽

Rate Constants ◽

Accommodation Coefficient ◽

Uptake Coefficient ◽

Flow Reactors ◽

Reactive Uptake Coefficient ◽

Fragmentation Reactions ◽

Gas Phase Fragmentation

Abstract. Oxidation flow reactors (OFRs) allow the concentration of a given atmospheric oxidant to be increased beyond ambient levels in order to study secondary organic aerosol (SOA) formation and aging over varying periods of equivalent aging by that oxidant. Previous studies have used these reactors to determine the bulk OA mass and chemical evolution. To our knowledge, no OFR study has focused on the interpretation of the evolving aerosol size distributions. In this study, we use size distribution measurements of the OFR and an aerosol microphysics model to learn about size-dependent processes in the OFR. Specifically, we use OFR exposures between 0.09–0.9 equivalent days of OH aging from the 2011 BEACHON-RoMBAS and the GoAmazon2014/5 field campaigns. We use simulations in the TOMAS (TwO-Moment Aerosol Sectional) microphysics box model to constrain the following parameters in the OFR: (1) the rate constant of gas-phase functionalization reactions of organic compounds with OH, (2) the rate constant of gas-phase fragmentation reactions of organic compounds with OH, (3) the reactive uptake coefficient for heterogeneous fragmentation reactions with OH, (4) the nucleation rate constants for three different nucleation schemes, and (5) an effective accommodation coefficient that accounts for possible particle diffusion limitations of particles larger than 60 nm in diameter. We find the best model-to-measurement agreement when the accommodation coefficient of the larger particles (Dp > 60 nm) was 0.1 or lower (with an accommodation coefficient of 1 for smaller particles), which suggests a diffusion limitation in the larger particles. When using these low accommodation-coefficient values, the model agrees with measurements when using a published H2SO4-organics nucleation mechanism and previously published values of rate constants for gas-phase oxidation reactions. Further, gas-phase fragmentation was found to have a significant impact upon the size distribution, and including fragmentation was necessary for accurately simulating the distributions in the OFR. The model was insensitive to the value of the reactive uptake coefficient on these aging timescales. Monoterpenes and isoprene could explain 24–95 % of the observed change in total volume of aerosol in the OFR, with ambient semivolatile and intermediate-volatility organic compounds (S/IVOCs) appearing to explain the remainder of the change in total volume. These results provide support to the mass-based findings of previous OFR studies, give insight to important size-distribution dynamics in the OFR, and enable the design of future OFR studies focused on new particle formation and/or microphysical processes.

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