Investigation of OH radical kinetics with glycine, alanine, serine and threonine in the aqueous phase

2021 ◽  
Author(s):  
Liang Wen ◽  
Thomas Schaefer ◽  
Hartmut Herrmann
Keyword(s):  
Amino Acids ◽  
Aqueous Phase ◽  
Rate Constants ◽  
Density Functional ◽  
Flash Photolysis ◽  
Biological Activities ◽  
Radical Reaction ◽  
Atmospheric Effects ◽  
Oh Radical ◽  
Kinetics Of

<p>Amino acids are key substances in biological activities and can be emitted into the atmosphere as constituents of primary aerosols. Understanding the radical kinetics of amino acids is necessary to evaluate their atmospheric effects. In the present study, the hydroxyl radical (OH) reaction kinetics of glycine, alanine, serine and threonine were investigated in the aqueous phase. The temperature and pH dependent rate constants were measured by a laser flash photolysis-long path absorption setup using the competition kinetics method. Based on the measurements and speciation calculations, the OH radical reaction rate constants of the fully protonated (H<sub>2</sub>A<sup>+</sup>) and neutral (HA<sup>±</sup>) form were determined. The following T-dependent Arrhenius expressions were derived for the OH radical reactions with glycine, <em>k</em>(<em>T</em>, H<sub>2</sub>A<sup>+</sup>) = (9.1 ± 0.3) × 10<sup>9</sup> × exp[(-2360 ± 230 K)/<em>T</em>], <em>k</em>(<em>T</em>, HA<sup>±</sup>) = (1.3 ± 0.1) × 10<sup>10</sup> × exp[(-2040 ± 240 K)/<em>T</em>]; alanine, <em>k</em>(<em>T</em>, H<sub>2</sub>A<sup>+</sup>) = (1.0 ± 0.1) × 10<sup>9</sup> × exp[(-1030 ± 340 K)/<em>T</em>], <em>k</em>(<em>T</em>, HA<sup>±</sup>) = (6.8 ± 0.4) × 10<sup>10</sup> × exp[(-2020 ± 370 K)/<em>T</em>]; serine, <em>k</em>(<em>T</em>, H<sub>2</sub>A<sup>+</sup>) = (1.1 ± 0.1) × 10<sup>9</sup> × exp[(-470 ± 150 K)/<em>T</em>], <em>k</em>(<em>T</em>, HA<sup>±</sup>) = (3.9 ± 0.1) × 10<sup>9</sup> × exp[(-720 ± 130 K)/<em>T</em>]; and threonine, <em>k</em>(<em>T</em>, H<sub>2</sub>A<sup>+</sup>) = (5.0 ± 0.1) × 10<sup>10</sup> × exp[(-1500 ± 100 K)/<em>T</em>], <em>k</em>(<em>T</em>, HA<sup>±</sup>) = (3.3 ± 0.1) × 10<sup>10</sup> × exp[(-1320 ± 90 K)/<em>T</em>] (in units of L mol<sup>-1</sup> s<sup>-1</sup>).</p> <p>The density functional theory calculation was performed using GAUSSIAN to simulate the energy barriers (<em>E<sub>Barrier</sub></em>) of OH radical induced H-atom abstraction. According to the simulated results, amino and carboxyl group increase the <em>E<sub>Barrier</sub></em> at the adjacent C‑atom and thus reduce the OH radical reactivity. Hydroxide and methyl group decrease the <em>E<sub>Barrier</sub></em> at the adjacent C-atom, leading to an increase in the OH radical rate constant.</p>

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>

Competition kinetics of OH radical reactions with oxygenated organic compounds in aqueous solution: rate constants and internal optical absorption effects

2018 ◽  
Vol 20 (16) ◽  
pp. 10939-10948 ◽  
Author(s):  
T. Schaefer ◽  
H. Herrmann
Keyword(s):  
Aqueous Solution ◽  
Optical Absorption ◽  
Organic Compounds ◽  
Aqueous Phase ◽  
Rate Constants ◽  
Radical Reactions ◽  
Solution Rate ◽  
Oh Radical ◽  
Kinetics Of

Atmospheric aqueous phase rate constants are determined and the effect of optical absorbers in competition kinetics is studied.

Reduction of hexaammineruthenium(III) ions by a series of tris(polypyridyl)chromium(II) ions – Revisiting the Cr(NN)33+/2+ self-exchange rate

2001 ◽  
Vol 79 (7) ◽  
pp. 1124-1127 ◽  
Author(s):  
K Omar Zahir
Keyword(s):  
Exchange Rate ◽  
Excited States ◽  
Rate Constants ◽  
Driving Force ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Outer Sphere ◽  
Laser Flash ◽  
Exchange Rate Constant ◽  
Kinetics Of

The kinetics of the outer-sphere oxidation of Cr(NN)32+ ions (NN = 2,2'-bipyridine, 1,10-phenanthroline, and their substituted analogs) by hexaammineruthenium(III) was studied using laser flash photolysis. The Cr(NN)32+ ions were generated via the reductive quenching of the *Cr(NN)33+ excited states by oxalate ions or by H2edta2–. The second-order rate constants were found to vary with the driving force of the reaction. The rate constants increase from (7.1 ± 0.5) × 106 M–1 s–1 for Cr(5-Clphen)32+ to (2.6 ± 0.2) × 108 M–1 s–1 for Cr(4,7-Me2phen)32+. The self-exchange rate constant for the couple (Cr(NN)33+/2+) was calculated by applying Marcus cross relation to present and other known reactions of Cr(NN)3n+ ions, where n = 3 or 2 with various reactants and is estimated to be (6 ± 4) × 107 M–1 s–1.Key words: tris(polypyridyl)chromium(II)/(III) self-exchange rate, hexaammineruthenium(III), oxidation of Cr(NN)32+.

Atmospheric oxidation mechanism of polyfluorinated sulfonamides — A quantum chemical and kinetic study

2013 ◽  
Vol 91 (6) ◽  
pp. 472-478 ◽  
Author(s):  
Xiaoyan Sun ◽  
Lei Ding ◽  
Qingzhu Zhang ◽  
Wenxing Wang
Keyword(s):  
Rate Constants ◽  
Density Functional ◽  
Single Point ◽  
Oxidation Mechanism ◽  
Basis Set ◽  
Atmospheric Oxidation ◽  
Oh Radicals ◽  
Oh Radical ◽  
Orbital Theory ◽  
Point Energy

Polyfluorinated sulfonamides (FSAs, F(CF2)nSO2NR1R2) are present in the atmosphere and may serve as the source of perfluorocarboxylates (PFCAs, CF3(CF2)nCOO–) in remote locations through long-range atmospheric transport and oxidation. Density functional theory (DFT) molecular orbital theory calculations were carried out to investigate OH radical-initiated atmospheric oxidation of a series of sulfonamides, F(CF2)nSO2NR1R2 (n = 4, 6, 8). Geometry optimizations of the reactants as well as the intermediates, transition states, and products were performed at the MPWB1K level with the 6-31G+(d,p) basis set. Single-point energy calculations were carried out at the MPWB1K/6-311+G(3df,2p) level of theory. The OH radical-initiated reaction mechanism is given and confirms that the OH addition to the sulfone double bond producing perfluoroalkanesulfonic acid directly cannot occur in the general atmosphere. Canonical variational transition-state (CVT) theory with small curvature tunneling (SCT) contribution was used to predict the rate constants. The overall rate constants were determined, k(T) (N-EtFBSA + OH) = (3.21 × 10−12) exp(–584.19/T), k(T) (N-EtFHxSA + OH) = (3.21 × 10−12) exp(–543.24/T), and k(T) (N-EtFOSA + OH) = (2.17 × 10−12) exp(–504.96/T) cm3 molecule−1 s−1, over the possible atmospheric temperature range of 180–370 K, indicating that the length of the F(CF2)n group has no large effect on the reactivity of FSAs. Results show that the atmospheric lifetime of FSAs determined by OH radicals will be 20–40 days, which agrees well with the experimental values (20–50 days), 20 thus they may contribute to the burden of perfluorinated pollution in remote regions.

Kinetics of OH Radical Reaction with Anthracene and Anthracene-d10

2006 ◽  
Vol 110 (10) ◽  
pp. 3559-3566 ◽  
Author(s):  
Rajeshwar Ananthula ◽  
Takahiro Yamada ◽  
Philip H. Taylor
Keyword(s):  
Radical Reaction ◽  
Oh Radical ◽  
Kinetics Of

scholarly journals Iron(III) hydroxocomplex - methyl viologen dication system as a prospective tool for determination of hydroxyl radical reaction rate constants with environmental pollutants

2021 ◽  
Author(s):  
Yuliya Tyutereva ◽  
Vyacheslav P. Grivin ◽  
Jing Xu ◽  
Feng Wu ◽  
Victor Plyusnin ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Rate Constants ◽  
Reaction Rate ◽  
Methyl Viologen ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Radical Reaction ◽  
Reaction Rate Constants ◽  
Wide Range

Abstract Reactivity of oxidative species with target pollutants is one of the crucial parameters for application of any system based on advanced oxidation processes (AOPs). This work presents new useful approach how to determine the hydroxyl radical reaction rate constants (kOH) using UVA laser flash photolysis technique. Fe(III) hydroxocomplex at pH 3 was applied as a standard source of hydroxyl radicals and methyl viologen dication (MV2+) was used as selective probe for •OH radical. Application of MV2+ allows to determine kOH values even for compounds which do not generate themselves optically detectable transient species in reaction with hydroxyl radicals. Validity of this approach was tested on a wide range of different persistent pesticides and its main advantages and drawbacks in comparison with existing steady-state and time-resolved techniques were discussed.

Kinetics of OH radical reaction with phenanthrene: New absolute rate measurements and comparison with other PAHs

2007 ◽  
Vol 39 (11) ◽  
pp. 629-637 ◽  
Author(s):  
Rajeshwar Ananthula ◽  
Takahiro Yamada ◽  
Philip H. Taylor
Keyword(s):  
Radical Reaction ◽  
Oh Radical ◽  
Absolute Rate ◽  
Kinetics Of
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