Computational study on OH radical reaction with CHF2CHFCHF2(HFC-245ea) between 200 and 400 K

2011 ◽  
Vol 43 (8) ◽  
pp. 418-430 ◽  
Author(s):  
Mohamad Akbar Ali ◽  
B. Rajakumar
Keyword(s):  
Computational Study ◽  
Radical Reaction ◽  
Oh Radical

2-Deoxyribose Radicals in the Gas Phase and Aqueous Solution. Transient Intermediates of Hydrogen Atom Abstraction from 2-Deoxyribofuranose

2005 ◽  
Vol 70 (11) ◽  
pp. 1769-1786 ◽  
Author(s):  
Luc A. Vannier ◽  
Chunxiang Yao ◽  
František Tureček
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Atom ◽  
Gas Phase ◽  
Computational Study ◽  
Hydrogen Atom Abstraction ◽  
Oh Radical ◽  
Free Energies ◽  
Intramolecular Hydrogen ◽  
Solvation Free Energies ◽  
Transient Intermediates

A computational study at correlated levels of theory is reported to address the structures and energetics of transient radicals produced by hydrogen atom abstraction from C-1, C-2, C-3, C-4, C-5, O-1, O-3, and O-5 positions in 2-deoxyribofuranose in the gas phase and in aqueous solution. In general, the carbon-centered radicals are found to be thermodynamically and kinetically more stable than the oxygen-centered ones. The most stable gas-phase radical, 2-deoxyribofuranos-5-yl (5), is produced by H-atom abstraction from C-5 and stabilized by an intramolecular hydrogen bond between the O-5 hydroxy group and O-1. The order of radical stabilities is altered in aqueous solution due to different solvation free energies. These prefer conformers that lack intramolecular hydrogen bonds and expose O-H bonds to the solvent. Carbon-centered deoxyribose radicals can undergo competitive dissociations by loss of H atoms, OH radical, or by ring cleavages that all require threshold dissociation or transition state energies >100 kJ mol-1. This points to largely non-specific dissociations of 2-deoxyribose radicals when produced by exothermic hydrogen atom abstraction from the saccharide molecule. Oxygen-centered 2-deoxyribose radicals show only marginal thermodynamic and kinetic stability and are expected to readily fragment upon formation.

Reaction kinetics of OH radicals with glutaric acid and adipic acid in the aqueous phase

2021 ◽  
Author(s):  
Liang Wen ◽  
Thomas Schaefer ◽  
Hartmut Herrmann
Keyword(s):  
Aqueous Phase ◽  
Adipic Acid ◽  
Rate Constants ◽  
Density Functional ◽  
Glutaric Acid ◽  
Radical Reaction ◽  
Basis Set ◽  
Oh Radicals ◽  
Oh Radical ◽  
Energy Barriers

<p>Dicarboxylic acids (DCAs) are widely distributed in atmospheric aerosols and cloud droplets and are mainly formed by the oxidation of volatile organic compounds (VOCs). For example, glutaric acid and adipic acid are two kinds of the DCAs that can be oxidized by hydroxyl radical (‧OH) reactions in the aqueous phase of aerosols and droplets. In the present study, the temperature- and pH-dependent rate constants of the aqueous OH radical reactions of the two DCAs were investigated by a laser flash photolysis-long path absorption setup using the competition kinetics method. Based on speciation calculations, the OH radical reaction rate constants of the fully protonated (H<sub>2</sub>A), deprotonated (HA<sup>-</sup>) and fully deprotonated (A<sup>2-</sup>) forms of the two DCAs were determined. The following Arrhenius expressions for the T-dependency of the OH radical reaction of glutaric acid, k(T, H<sub>2</sub>A) = (3.9 ± 0.1) × 10<sup>10</sup> × exp[(-1270 ± 200 K)/T], k(T, HA<sup>-</sup>) = (2.3 ± 0.1) × 10<sup>11</sup> × exp[(-1660 ± 190 K)/T], k(T, A<sup>2-</sup>) = (1.4 ± 0.1) × 10<sup>11</sup> × exp[(-1400 ± 170 K)/T] and adipic acid, k(T, H<sub>2</sub>A) = (7.5 ± 0.2) × 10<sup>10</sup> × exp[(-1210 ± 170 K)/T], k(T, HA<sup>-</sup>) = (9.5 ± 0.3) × 10<sup>10</sup> × exp[(-1200 ± 200 K)/T], k(T, A<sup>2-</sup>) = (8.7 ± 0.2) × 10<sup>10</sup> × exp[(-1100 ± 170 K)/T] (in unit of L mol<sup>-1</sup> s<sup>-1</sup>) were derived.</p><p>The energy barriers of the H-atom abstractions were simulated by the Density Functional Theory calculations run with the GAUSSIAN package using the M06-2X method and the basis set m062x/6-311++g(3df,2p). The results showed that the energy barriers were lower at the C<sub>β</sub>-atoms and are higher at the C<sub>α</sub>-atoms of the two DCAs, clearly suggesting that the H-atom abstractions occurred predominately at the C<sub>β</sub>-atoms. In addition, the ionizations can enhance the electrostatic effects of the carboxyl groups, significantly reducing the energy barriers, leading to the order of OH radical reactivity as  <  < . This study intends to better characterize the losing processes of glutaric acid and adipic acid in atmospheres.</p>

Investigation of the formation of acid rain based on the sulfur tetroxide (SO4 (C2v)) and OH radical reaction

2012 ◽  
Vol 23 (5) ◽  
pp. 1609-1615 ◽  
Author(s):  
Moein Goodarzi ◽  
Morteza Vahedpour ◽  
Mohammad Solimannejad
Keyword(s):  
Acid Rain ◽  
Radical Reaction ◽  
Oh Radical

scholarly journals Importance of SOA formation of α-pinene, limonene and <i>m</i>-cresol comparing day-and night-time radical chemistry

2020 ◽  
Author(s):  
Anke Mutzel ◽  
Yanli Zhang ◽  
Olaf Böge ◽  
Maria Rodigast ◽  
Agata Kolodziejczyk ◽  
...  
Keyword(s):  
Mass Fraction ◽  
Radical Reaction ◽  
Water Soluble ◽  
Oh Radicals ◽  
Oh Radical ◽  
Night Time ◽  
Formation Potential ◽  
Phase Constituent ◽  
Dry Conditions ◽  
The One

Abstract. The oxidation of biogenic and anthropogenic compounds leads to the formation of secondary organic aerosol mass (SOA). The present study aims to investigate α-pinene, limonene and m-cresol with regards to their SOA formation potential dependent on relative humidity (RH) under night- (NO3 radicals) and day-time conditions (OH radicals) and the resulting chemical composition. It was found that SOA formation potential of limonene with NO3 significantly exceeds the one of the OH radical reaction, with SOA yields of 15–30 % and 10–21 %, respectively. Additionally, the nocturnal SOA yield was found to be very sensitive towards RH, yielding more SOA under dry conditions. On the contrary, the SOA formation potential of α-pinene with NO3 slightly exceeds that of the OH radical reaction, independent from RH. In average, α-pinene yielded SOA with about 6–7 % from NO3 radicals and 3–4 % from OH radical reaction. Surprisingly, unexpected high SOA yields were found for m-cresol oxidation with OH radicals (3–9 %) with the highest yield under elevated RH (9 %) which is most likely attributed to a higher fraction of 3-methyl-6-nitro-catechol (MNC). While α-pinene and m-cresol SOA was found to be mainly composed of water-soluble compounds, 50–68 % of nocturnal SOA and 22–39 % of daytime limonene SOA is water-insoluble. The fraction of SOA-bound peroxides which originated from α-pinene varied between 2–80 % as a function of RH. Furthermore, SOA from α-pinene revealed pinonic acid as the most important particle-phase constituent under day- and night-time conditions with fraction of 1–4 %. Further compounds detected are norpinonic acid (0.05–1.1 % mass fraction), terpenylic acid (0.1–1.1 % mass fraction), pinic acid (0.1–1.8 % mass fraction) and 3-methyl-1,2,3-tricarboxylic acid (0.05–0.5 % mass fraction). All marker compounds showed higher fractions under dry conditions when formed during daytime and almost no RH effect when formed during night.

Computational study on the reaction of CH3SCH2CH3 with OH radical: mechanism and enthalpy of formation

2011 ◽  
Vol 129 (6) ◽  
pp. 771-780 ◽  
Author(s):  
Jia Cao ◽  
Wenliang Wang ◽  
Yue Zhang ◽  
Weina Wang ◽  
Tianlei Zhang ◽  
...  
Keyword(s):  
Enthalpy Of Formation ◽  
Computational Study ◽  
Radical Mechanism ◽  
Oh Radical
Sign in / Sign up

Export Citation Format

Share Document