Atmospheric fate of hydrofluoroethanes and hydrofluorochloroethanes: 1. Rate coefficients for reactions with OH

1991 ◽  
Vol 96 (D3) ◽  
pp. 5001 ◽  
Author(s):  
Tomasz Gierczak ◽  
Ranajit Talukdar ◽  
Ghanshyam L. Vaghjiani ◽  
Edward R. Lovejoy ◽  
A. R. Ravishankara
Keyword(s):  
Rate Coefficients ◽  
Atmospheric Fate

ChemInform Abstract: Atmospheric Fate of CF2H2, CH3CF3, CHF2CF3, and CH3CFCl2: Rate Coefficients for Reactions with OH and UV Absorption Cross Sections of CH3CFCl2.

ChemInform ◽  
2010 ◽  
Vol 22 (42) ◽  
pp. no-no
Author(s):  
R. TALUKDAR ◽  
A. MELLOUKI ◽  
T. GIERCZAK ◽  
J. B. BURKHOLDER ◽  
S. A. MCKEEN ◽  
...  
Keyword(s):  
Cross Sections ◽  
Uv Absorption ◽  
Rate Coefficients ◽  
Absorption Cross ◽  
Atmospheric Fate

scholarly journals Atmospheric fate of a series of saturated alcohols: kinetic and mechanistic study

2020 ◽  
Vol 20 (2) ◽  
pp. 699-720
Author(s):  
Inmaculada Colmenar ◽  
Pilar Martin ◽  
Beatriz Cabañas ◽  
Sagrario Salgado ◽  
Araceli Tapia ◽  
...  
Keyword(s):  
Carbon Chain ◽  
Rate Coefficients ◽  
Mechanistic Study ◽  
Oh Radicals ◽  
Reaction Products ◽  
Atmospheric Fate ◽  
No3 Radical ◽  
Oh Reactions ◽  
Polyfunctional Compounds ◽  
Cl Atoms

Abstract. The atmospheric fate of a series of saturated alcohols (SAs) was evaluated through kinetic and reaction product studies with the main atmospheric oxidants. These SAs are alcohols that could be used as fuel additives. Rate coefficients (in cm3 molecule−1 s−1) measured at ∼298 K and atmospheric pressure (720±20 Torr) were as follows: k1 ((E)-4-methylcyclohexanol + Cl) = (3.70±0.16) ×10-10, k2 ((E)-4-methylcyclohexanol + OH) = (1.87±0.14) ×10-11, k3 ((E)-4-methylcyclohexanol + NO3) = (2.69±0.37) ×10-15, k4 (3,3-dimethyl-1-butanol + Cl) = (2.69±0.16) ×10-10, k5 (3,3-dimethyl-1-butanol + OH) = (5.33±0.16) ×10-12, k6 (3,3-dimethyl-2-butanol + Cl) = (1.21±0.07) ×10-10, and k7 (3,3-dimethyl-2-butanol + OH) = (10.50±0.25) ×10-12. The main products detected in the reaction of SAs with Cl atoms (in the absence/presence of NOx), OH radicals, and NO3 radicals were (E)-4-methylcyclohexanone for the reactions of (E)-4-methylcyclohexanol, 3,3-dimethylbutanal for the reactions of 3,3-dimethyl-1-butanol, and 3,3-dimethyl-2-butanone for the reactions of 3,3-dimethyl-2-butanol. Other products such as formaldehyde, 2,2-dimethylpropanal, and acetone have also been identified in the reactions of Cl atoms and OH radicals with 3,3-dimethyl-1-butanol and 3,3-dimethyl-2-butanol. In addition, the molar yields of the reaction products were estimated. The products detected indicate a hydrogen atom abstraction mechanism at different sites on the carbon chain of alcohol in the case of Cl reactions and a predominant site in the case of OH and NO3 reactions, confirming the predictions of structure–activity relationship (SAR) methods. Tropospheric lifetimes (τ) of these SAs have been calculated using the experimental rate coefficients. Lifetimes are in the range of 0.6–2 d for OH reactions, 7–13 d for NO3 radical reactions, and 1–3 months for Cl atoms. In coastal areas, the lifetime due to the reaction with Cl decreases to hours. The calculated global tropospheric lifetimes, and the polyfunctional compounds detected as reaction products in this work, imply that SAs could contribute to the formation of ozone and nitrated compounds at local, regional, and even global scales. Therefore, the use of saturated alcohols as additives in diesel blends should be considered with caution.

scholarly journals Atmospheric fate of a series of Methyl Saturated Alcohols (MSA): Kinetic and Mechanistic study

2019 ◽  
Author(s):  
Inmaculada Colmenar ◽  
Pilar Martin ◽  
Beatriz Cabañas ◽  
Sagrario Salgado ◽  
Araceli Tapia ◽  
...  
Keyword(s):  
Hydrogen Abstraction ◽  
Global Scale ◽  
Rate Coefficients ◽  
Mechanistic Study ◽  
Oh Radical ◽  
Reaction Products ◽  
Atmospheric Fate ◽  
No3 Radical ◽  
Oh Reactions ◽  
Polyfunctional Compounds

Abstract. The atmospheric fate of a series of Methyl Saturated Alcohols (MSA) has been evaluated through the kinetic and reaction product studies with the main atmospheric oxidants. Rate coefficients (in cm3 molecule−1 s−1 unit) measured at ~ 298 K and atmospheric pressure (~ 740 Torr) were as follows: (3.71 ± 0.53) × 10−10, (1.91 ± 0.65) × 10−11 and (2.92 ± 1.38) × 10−15 for reaction of E-4-methyl-cyclohexanol with Cl, OH and NO3, respectively. (2.70 ± 0.55) × 10−10 and (5.57 ± 0.66) × 10−12 for reaction of 3,3-dimethyl-1-butanol with Cl and OH radical respectively and (1.21 ± 0.37) × 10−10 and (10.51 ± 0.81) × 10−12 for reaction of 3,3-dimethyl-2-butanol with Cl and OH radical respectively. The main detected products were 4-methylcyclohexanone, 3,3-dimethylbutanal and 3,3-dimethyl-2-butanone for the reactions of E-4-methyl-cyclohexanol, 3,3-dimethyl-1-butanol and 3,3-dimethyl-2-butanol respectively with the three oxidants. A tentative estimation of yields have been done obtaining the following ranges (25–60) % for 4-methylcyclohexanone, (40–60) % for 3,3-dimethylbutanal and (40–80) % for 3,3-dimethyl-2-butanone. Other products as HCOH, 2,2-dimethylpropanal and acetone have been identified in the reaction of 3,3-dimethyl-1-butanol and 3,3-dimethyl-2-butanol. The yields of these products indicate a hydrogen abstraction mechanism at different sites of the alkyl chain in the case of Cl reaction and a predominant site in the case of OH and NO3 reactions, supported by SAR methods prediction. Tropospheric lifetimes (τ) of these MSA have been calculated using the experimental rate coefficients. Lifetimes are in the range of 0.6–2 days for OH reactions, 8–13 days for NO3 radical reactions and 1–3 months for Cl atoms. In coastal areas the lifetime due to the reaction with Cl decreases to hours. The global tropospheric lifetimes calculated, and the polyfunctional compounds detected as reaction products in this work, imply that the Methyl Saturated Alcohols could contribute to ozone and nitrated compound formation at local, but also regional and even to global scale. Therefore, the use of large saturated alcohols as additives in biofuels must be taken with caution.

A New AID for Interpolating and Assessing Collision Strengths and Rate Coefficients

1988 ◽  
Vol 102 ◽  
pp. 107-110
Author(s):  
A. Burgess ◽  
H.E. Mason ◽  
J.A. Tully
Keyword(s):  
Significant Loss ◽  
Impact Excitation ◽  
Rate Coefficients ◽  
Electron Impact Excitation ◽  
Graphical Display ◽  
Practical Procedure ◽  
Positive Ions ◽  
Allowed Transition ◽  
Computational Errors ◽  
Existing Data

AbstractA new way of critically assessing and compacting data for electron impact excitation of positive ions is proposed. This method allows one (i) to detect possible printing and computational errors in the published tables, (ii) to interpolate and extrapolate the existing data as a function of energy or temperature, and (iii) to simplify considerably the storage and transfer of data without significant loss of information. Theoretical or experimental collision strengths Ω(E) are scaled and then plotted as functions of the colliding electron energy, the entire range of which is conveniently mapped onto the interval (0,1). For a given transition the scaled Ω can be accurately represented - usually to within a fraction of a percent - by a 5 point least squares spline. Further details are given in (2). Similar techniques enable thermally averaged collision strengths upsilon (T) to be obtained at arbitrary temperatures in the interval 0 < T < ∞. Application of the method is possible by means of an interactive program with graphical display (2). To illustrate this practical procedure we use the program to treat Ω for the optically allowed transition 2s → 2p in ArXVI.

Electron impact excitation of Al XIII : Collision strengths and rate coefficients

2001 ◽  
Vol 11 (PR2) ◽  
pp. Pr2-309-Pr2-312
Author(s):  
K. M. Aggarwal ◽  
F. P. Keenan ◽  
S. J. Rose
Keyword(s):  
Electron Impact ◽  
Impact Excitation ◽  
Rate Coefficients ◽  
Electron Impact Excitation

THE IONIZATION RATE COEFFICIENTS FOR SOME RADIATIVELY EXCITED RUBIDIUM STATES

1979 ◽  
Vol 40 (C7) ◽  
pp. C7-87-C7-88
Author(s):  
A. N. Klucharev ◽  
A. V. Lazarenko ◽  
V. Vujnovic
Keyword(s):  
Ionization Rate ◽  
Rate Coefficients

Photoinduced Charge Transfer Dynamics in Carotenoid-Porphyrin-C60 Triad via the Linearized Semiclassical Nonequilibrium Fermi's Golden Rule

2020 ◽  
Author(s):  
Zhengqing Tong ◽  
Margaret S. Cheung ◽  
Barry D. Dunietz ◽  
Eitan Geva ◽  
Xiang Sun
Keyword(s):  
Charge Transfer ◽  
Golden Rule ◽  
Time Dependent ◽  
Rate Coefficients ◽  
Initial State ◽  
Photoinduced Charge Transfer ◽  
Transfer Rates ◽  
Fermi's Golden Rule ◽  
Photoinduced Charge ◽  
Fermi’S Golden Rule

The nonequilibrium Fermi’s golden rule (NE-FGR) describes the time-dependent rate coefficient for electronic transitions, when the nuclear degrees of freedom start out in a <i>nonequilibrium</i> state. In this letter, the linearized semiclassical (LSC) approximation of the NE-FGR is used to calculate the photoinduced charge transfer rates in the carotenoid-porphyrin-C<sub>60</sub> molecular triad dissolved in explicit tetrahydrofuran. The initial nonequilibrium state corresponds to impulsive photoexcitation from the equilibrated ground-state to the ππ* state, and the porphyrin-to-C<sub>60</sub> and the carotenoid-to-C<sub>60</sub> charge transfer rates are calculated. Our results show that accounting for the nonequilibrium nature of the initial state significantly enhances the transition rate of the porphyrin-to-C<sub>60</sub> CT process. We also derive the instantaneous Marcus theory (IMT) from LSC NE-FGR, which casts the CT rate coefficients in terms of a Marcus-like expression, with explicitly time-dependent reorganization energy and reaction free energy. IMT is found to reproduce the CT rates in the system under consideration remarkably well.

Reactivity Trends in the Gas Phase Addition of Acetylene to N-protonated Aryl Radical Cations

2020 ◽  
Author(s):  
Oisin Shiels ◽  
P. D. Kelly ◽  
Cameron C. Bright ◽  
Berwyck L. J. Poad ◽  
Stephen Blanksby ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ion Trap ◽  
Radical Cations ◽  
Rate Coefficients ◽  
Similar Process ◽  
Ion Molecule Reactions ◽  
Aromatic Radicals ◽  
Polycyclic Aromatic ◽  
Gas Phase Ion ◽  
Type Radical

<div> <div> <div> <p>A key step in gas-phase polycyclic aromatic hydrocarbon (PAH) formation involves the addition of acetylene (or other alkyne) to σ-type aromatic radicals, with successive additions yielding more complex PAHs. A similar process can happen for N- containing aromatics. In cold diffuse environments, such as the interstellar medium, rates of radical addition may be enhanced when the σ-type radical is charged. This paper investigates the gas-phase ion-molecule reactions of acetylene with nine aromatic distonic σ-type radical cations derived from pyridinium (Pyr), anilinium (Anl) and benzonitrilium (Bzn) ions. Three isomers are studied in each case (radical sites at the ortho, meta and para positions). Using a room temperature ion trap, second-order rate coefficients, product branching ratios and reaction efficiencies are reported. </p> </div> </div> </div>

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