scholarly journals Photochemical degradation of isoprene-derived 4,1-nitrooxy enal

2016 ◽  
Vol 16 (9) ◽  
pp. 5595-5610 ◽  
Author(s):  
Fulizi Xiong ◽  
Carlos H. Borca ◽  
Lyudmila V. Slipchenko ◽  
Paul B. Shepson
Keyword(s):  
First Generation ◽  
Degradation Process ◽  
Reaction Chamber ◽  
High Reactivity ◽  
Uv Absorption ◽  
Ionization Mass ◽  
Photochemical Degradation ◽  
Photolysis Frequency ◽  
Isoprene Oxidation ◽  
Uv Absorption Spectrum

Abstract. In isoprene-impacted environments, carbonyl nitrates are produced from NO3-initiated isoprene oxidation, which constitutes a potentially important NOx reservoir. To better understand the fate of isoprene carbonyl nitrates, we synthesized a model compound, trans-2-methyl-4-nitrooxy-2-buten-1-al (4,1-isoprene carbonyl nitrate, or 4,1-isoprene nitrooxy enal), and investigated its photochemical degradation process. The measured OH and O3 oxidation rate constants (298 K) for this nitrooxy enal are 4.1(±0.7)  ×  10−11 cm3 molecules−1 s−1 and 4.4(±0.3)  ×  10−18 cm3 molecules−1 s−1, respectively. Its UV absorption spectrum was determined, and the result is consistent with TDDFT calculations. Based on its UV absorption cross section and photolysis frequency in a reaction chamber, we estimate that the ambient photolysis frequency for this compound is 3.1(±0.8)  ×  10−4 s−1 for a solar zenith angle of 45°. The fast photolysis rate and high reactivity toward OH lead to a lifetime of less than 1 h for the isoprene nitrooxy enal, with photolysis being a dominant daytime sink. The nitrate products derived from the OH oxidation and the photolysis of the nitrooxy enal were identified with an iodide-based chemical ionization mass spectrometer. For the OH oxidation reaction, we quantified the yields of two nitrate products, methyl vinyl ketone nitrate and ethanal nitrate, which together contributed to 36(±5) % of the first-generation products.

scholarly journals Photochemical Degradation of Isoprene-derived 4,1-Carbonyl Nitrate

2016 ◽  
Author(s):  
F. Xiong ◽  
C. H. Borca ◽  
L. V. Slipchenko ◽  
P. B. Shepson
Keyword(s):  
First Generation ◽  
Degradation Process ◽  
Reaction Chamber ◽  
High Reactivity ◽  
Uv Absorption ◽  
Ionization Mass ◽  
Photochemical Degradation ◽  
Photolysis Frequency ◽  
Isoprene Oxidation ◽  
Uv Absorption Spectrum

Abstract. In isoprene-impacted environments, carbonyl nitrates are produced from NO3-initiated isoprene oxidation, which constitutes a potentially important NOx reservoir. To better understand the fate of isoprene carbonyl nitrates, we synthesized a model compound, trans-nitrooxy-2-methyl-2-buten-1-al (4,1-isoprene carbonyl nitrate) and investigated its photochemical degradation process. The measured OH and O3 oxidation rate constants for this carbonyl nitrate are 4.1 (±0.7) × 10−11 cm3 molecules−1 s−1 and 4.4 (±0.3) × 10−18 cm3 molecules−1 s−1. The UV absorption spectrum of the carbonyl nitrate was determined, and the result is consistent with TDDFT calculations. Based on its UV absorption cross section and photolysis frequency in a reaction chamber, we estimate that the ambient photolysis frequency for this compound is 3.1 × 10−4 s−1 for a solar zenith angle (SZA) of 45°. The fast photolysis rate and high reactivity toward OH lead to a lifetime of less than one hour for the carbonyl nitrate, with photolysis being a dominant daytime sink. The nitrate products derived from the OH oxidation and the photolysis of the isoprene carbonyl nitrate were identified with an iodide-based chemical ionization mass spectrometer. For the OH oxidation reaction, we quantified the yields of two nitrate products, MVK nitrate and ethanal nitrate, which together contributed to 37 (±5) % of the first-generation products.

scholarly journals Investigation of the β-pinene photooxidation by OH in the atmosphere simulation chamber SAPHIR

2016 ◽  
Author(s):  
Martin Kaminski ◽  
Hendrik Fuchs ◽  
Ismail-Hakki Acir ◽  
Birger Bohn ◽  
Theo Brauers ◽  
...  
Keyword(s):  
Degradation Mechanism ◽  
Degradation Process ◽  
Product Distribution ◽  
High Reactivity ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Emission Rates ◽  
Photochemical Degradation ◽  
Atmosphere Simulation Chamber ◽  
Simulation Chamber

Abstract. Beside isoprene, monoterpenes are the non-methane volatile organic compounds (VOC) with the highest global emission rates. Due to their high reactivity towards OH, monoterpenes can dominate the radical chemistry of the atmosphere in forested areas. In the present study the photochemical degradation mechanism of β-pinene was investigated in the Jülich atmosphere simulation chamber SAPHIR. The focus of this study is on the OH budget in the degradation process. Therefore the SAPHIR chamber was equipped with instrumentation to measure radicals (OH, HO2, RO2), the total OH reactivity, important OH precursors (O3, HONO, HCHO), the parent VOC beta-pinene, its main oxidation products, acetone and nopinone, and photolysis frequencies. All experiments were carried out under low NOx conditions (≤ 2 ppb) and at atmospheric beta-pinene concentrations (≤ 5 ppb) with and without addition of ozone. For the investigation of the OH budget, the OH production and destruction rates were calculated from measured quantities. Within the limits of accuracy of the instruments, the OH budget was balanced in all β-pinene oxidation experiments. However, even though the OH budget was closed, simulation results from the Master Chemical Mechanism 3.2 showed that the OH production and destruction rates were underestimated by the model. The measured OH and HO2 concentrations were underestimated by up to a factor of two whereas the total OH reactivity was slightly overestimated because of the poor reproduction of the measured nopinone by the model by up to a factor of three. A new, theory-derived first-generation product distribution by Vereecken and Peeters was able to reproduce the measured nopinone time series and the total OH reactivity. Nevertheless the measured OH and HO2 concentrations remained underestimated by the numerical simulations. These observations together with the fact that the measured OH budget was closed suggest the existence of unaccounted sources of HO2.

scholarly journals Kinetics of the reactions of isoprene-derived hydroxynitrates: gas phase epoxide formation and solution phase hydrolysis

2014 ◽  
Vol 14 (8) ◽  
pp. 12121-12165 ◽  
Author(s):  
M. I. Jacobs ◽  
W. J. Burke ◽  
M. J. Elrod
Keyword(s):  
Gas Phase ◽  
Hydrolysis Rate ◽  
Ionization Mass ◽  
Volatile Organic ◽  
Isoprene Oxidation ◽  
Gas Phase Oxidation ◽  
Acid Catalyzed ◽  
Regional Formation ◽  
A Minor ◽  
Kinetics Of

Abstract. Isoprene, the most abundant non-methane volatile organic compound (VOC) emitted into the atmosphere, is known to undergo gas phase oxidation to form eight different hydroxynitrate isomers in "high NOx" environments. These hydroxynitrates are known to affect the global and regional formation of ozone and secondary organic aerosol (SOA), as well as affect the distribution of nitrogen. In the present study, we have synthesized three of the eight possible hydroxynitrates: 4-hydroxy-3-nitroxy isoprene (4,3-HNI) and E/Z-1-hydroxy-4-nitroxy isoprene (1,4-HNI). Oxidation of the 4,3-HNI isomer by the OH radical was monitored using a flow tube chemical ionization mass spectrometer (FT-CIMS), and its OH rate constant was determined to be (3.64 ± 0.41) × 10−11 cm3 molecule−1 s−1. The products of 4,3-HNI oxidation were monitored, and a mechanism to explain the products was developed. An isoprene epoxide (IEPOX) – a species important in SOA chemistry and thought to originate only from "low NOx" isoprene oxidation – was found as a minor, but significant product. Additionally, hydrolysis kinetics of the three synthesized isomers were monitored with NMR. The bulk, neutral solution hydrolysis rate constants for 4,3-HNI and the 1,4-HNI isomers were (1.59±0.03 × 10−5 s−1 and (6.76 ± 0.09) × 10−3 s−1, respectively. The hydrolysis reactions of each isomer were found to be general acid-catalyzed. The reaction pathways, product yields and atmospheric implications for both the gas phase and aerosol-phase reactions are discussed.

scholarly journals EFFECT OF RADICAL SCAVENGERS AND PROPOSED PATHWAYS FOR DEGRADATION OF AZO DYE IN AQUEOUS SOLUTION UNDER PRESENCE OF IRON(III) AND PERSULPHATE

2017 ◽  
Vol 60 (4) ◽  
pp. 88
Author(s):  
Heng Zhong ◽  
Hui Zhao ◽  
Jun Li ◽  
Lei Sun ◽  
Aihua Xu ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Carboxylic Acids ◽  
Azo Dye ◽  
Water Discharge ◽  
Radical Scavenging ◽  
Degradation Process ◽  
Ionization Mass ◽  
Radical Scavengers ◽  
Acid Orange 7 ◽  
Degradation Of Azo Dye

The degradation process of Acid Orange 7 (AO7) in aqueous solutions by iron(III) under activation by persulfate (PS, S2O82-) oxidation and Visible (Vis) light (≥420 nm) exposure has been studied. The radical scavenging effect was examined by using ethanol (EtOH), tert-butyl alcohol (TBA) and sodium azide to state that the hydroxyl radical (·OH) is regarded as the predominant reactive oxidant for the AO7 decolorization, while the sulfate radical (SO4·-) and singlet oxygen(1O2) are also make their contribution to dye's degradation. The reaction intermediates were determined by electrospray ionization-mass spectrometry (ESI-MS) analysis, and a probable degradation pathway mechanism has been proposed. It was suggested, that firstly an initial successive radical attacks the N atom of the dye, which decompose to p-phenolsulfonic acid and 1,2-naphthaquinone through the contemporaneous break of two C-N bonds. Afterwards, subsequent oxidation of these products and loss of the −SO3− group are observed. Finally, the acyclic carboxylic acids are formed from the central ring-opening, and then the further oxidation to simple carboxylic acids is evident. The work can provide a simple, effective and economic system for the treatment of non-biodegradable azo dye. The recommendations were proposed on organization of an effective quality control of technological water discharge and products of its processing at the local wastewater treatment facilities of industrial plants for prevention of the ingress of hazardous biological substances to the hydrosphere.Forcitation:Heng Zhong, Hui Zhao, Jun Li, Lei Sun, Aihua Xu, Dongsheng Xia, Nevsky A.V. Effect of radical scavengers and proposed pathways for degradation of azo dye in aqueous solution under presence of iron (III) and persulphate. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 4. P. 88-94.

scholarly journals Isoprene oxidation by nitrate radical: alkyl nitrate and secondary organic aerosol yields

2009 ◽  
Vol 9 (2) ◽  
pp. 8857-8902 ◽  
Author(s):  
A. W. Rollins ◽  
A. Kiendler-Scharr ◽  
J. Fry ◽  
T. Brauers ◽  
S. S. Brown ◽  
...  
Keyword(s):  
First Generation ◽  
Secondary Organic Aerosol ◽  
Model Simulation ◽  
Effective Rate Constant ◽  
Organic Aerosol ◽  
Effective Rate ◽  
Oxidation Products ◽  
Alkyl Nitrates ◽  
Alkyl Nitrate ◽  
Isoprene Oxidation

Abstract. Alkyl nitrates and secondary organic aerosol (SOA) produced during the oxidation of isoprene by nitrate radicals has been observed in the SAPHIR chamber. We find the yield of nitrates is 70±8% from the isoprene+NO3 reaction, and the yield for secondary dinitrates produced in the reaction of primary isoprene nitrates with NO3 is 40±20%. We find an effective rate constant for reaction of NO3 with the group of first generation oxidation products to be 7×10−14 cm3 s−1. At the low total organic aerosol concentration in the chamber (max ≈0.6 μg m−3) we observed a mass yield (ΔSOA mass/Δisoprene mass) of 2% for the entire 16 h experiment. However a comparison of the timing of the observed SOA production to a box model simulation of first and second generation oxidation products shows that the yield from the first generation products was <0.2% while the further oxidation of the initial products leads to a yield of 10% (defined as ΔSOA/Δisoprene2x where Δisoprene2x is the mass of isoprene which reacted twice with NO3). The SOA yield of 10% is consistent with equilibrium partitioning of highly functionalized C5 products of isoprene oxidation.

UV absorption spectrum and absorption cross sections of COF2at 296 K in the range 200 - 230 nm

1992 ◽  
Vol 19 (3) ◽  
pp. 281-284 ◽  
Author(s):  
Andreas Nölle ◽  
Horst Heydtmann ◽  
Richard Meller ◽  
Wolfgang Schneider ◽  
Geert K. Moortgat
Keyword(s):  
Absorption Spectrum ◽  
Cross Sections ◽  
Uv Absorption ◽  
Absorption Cross ◽  
Uv Absorption Spectrum

scholarly journals Isolation and Structure Determination of Echinochrome A Oxidative Degradation Products

Molecules ◽  
2020 ◽  
Vol 25 (20) ◽  
pp. 4778
Author(s):  
Natalia P. Mishchenko ◽  
Elena A. Vasileva ◽  
Andrey V. Gerasimenko ◽  
Valeriya P. Grigorchuk ◽  
Pavel S. Dmitrenok ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Degradation Products ◽  
Lethal Dose ◽  
Oxidative Degradation ◽  
Degradation Process ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Ionization Mass ◽  
Echinochrome A ◽  
Esi Ms

Echinochrome A (Ech A, 1) is one of the main pigments of several sea urchin species and is registered in the Russian pharmacopeia as an active drug substance (Histochrome®), used in the fields of cardiology and ophthalmology. In this study, Ech A degradation products formed during oxidation by O2 in air-equilibrated aqueous solutions were identified, isolated, and structurally characterized. An HPLC method coupled with diode-array detection (DAD) and mass spectrometry (MS) was developed and validated to monitor the Ech A degradation process and identify the appearing compounds. Five primary oxidation products were detected and their structures were proposed on the basis of high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) as 7-ethyl-2,2,3,3,5,7,8-heptahydroxy-2,3-dihydro-1,4-naphthoquinone (2), 6-ethyl-5,7,8-trihydroxy-1,2,3,4-tetrahydronaphthalene-1,2,3,4-tetraone (3), 2,3-epoxy-7-ethyl-2,3-dihydro-2,3,5,6,8-pentahydroxy-1,4-naphthoquinone (4), 2,3,4,5,7-pentahydroxy-6-ethylinden-1-one (5), and 2,2,4,5,7-pentahydroxy-6-ethylindane-1,3-dione (6). Three novel oxidation products were isolated, and NMR and HR-ESI-MS methods were used to establish their structures as 4-ethyl-3,5,6-trihydroxy-2-oxalobenzoic acid (7), 4-ethyl-2-formyl-3,5,6-trihydroxybenzoic acid (8), and 4-ethyl-2,3,5-trihydroxybenzoic acid (9). The known compound 3-ethyl-2,5-dihydroxy-1,4-benzoquinone (10) was isolated along with products 7–9. Compound 7 turned out to be unstable; its anhydro derivative 11 was obtained in two crystal forms, the structure of which was elucidated using X-ray crystallography as 7-ethyl-5,6-dihydroxy-2,3-dioxo-2,3-dihydrobenzofuran-4-carboxylic acid and named echinolactone. The chemical mechanism of Ech A oxidative degradation is proposed. The in silico toxicity of Ech A and its degradation products 2 and 7–10 were predicted using the ProTox-II webserver. The predicted median lethal dose (LD50) value for product 2 was 221 mg/kg, and, for products 7–10, it appeared to be much lower (≥2000 mg/kg). For Ech A, the predicted toxicity and mutagenicity differed from our experimental data.

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