Kinetics and Mechanisms of the OH Radical Initiated Oxidation of Volatile Organic Compounds Under Simulated Tropospheric Conditions PDF Download
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Author: Jürg Ernst Eberhard
Publisher:
ISBN:
Category :
Languages : en
Pages : 93
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Author: Jürg Ernst Eberhard
Publisher:
ISBN:
Category :
Languages : en
Pages : 93
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Author: Konrad Stemmler
Publisher:
ISBN:
Category :
Languages : en
Pages : 168
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Author: Georges Le Bras
Publisher: Springer Science & Business Media
ISBN: 3642592163
Category : Science
Languages : en
Pages : 316
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Book Description
Oxidation and removal of atmospheric constituents involve complex sequences of reactions which can lead to the production of photo-oxidants such as ozone. In order to understand and model these complex reaction sequences, it is necessary to have a comprehensive understanding of reaction mechanisms and accurate estimates of kinetic parameters for relevant gas-phase atmospheric reactions. This book presents recent advances in the field and includes the following topics: e.g. the oxidation of simple organic compounds, NOx kinetics and mechanisms, OH radical production and rate constants for the OH attack on more complex organic compounds, peroxy and alkoxy radical reactions, photo-oxidation of aromatic and biogenic compounds, and the interaction between radical species.
Author: Jack Calvert
Publisher: Oxford University Press
ISBN: 0199877475
Category : Science
Languages : en
Pages : 1634
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Prepared by an international team of eminent atmospheric scientists, Mechanisms of Atmospheric Oxidation of the Oxygenates is an authoritative source of information on the role of oxygenates in the chemistry of the atmosphere. The oxygenates, including the many different alcohols, ethers, aldehydes, ketones, acids, esters, and nitrogen-atom containing oxygenates, are of special interest today due to their increased use as alternative fuels and fuel additives. This book describes the physical properties of oxygenates, as well as the chemical and photochemical parameters that determine their reaction pathways in the atmosphere. Quantitative descriptions of the pathways of the oxygenates from release or formation in the atmosphere to final products are provided, as is a comprehensive review and evaluation of the extensive kinetic literature on the atmospheric chemistry of the different oxygenates and their many halogen-atom substituted analogues. This book will be of interest to modelers of atmospheric chemistry, environmental scientists and engineers, and air quality planning agencies as a useful input for development of realistic modules designed to simulate the atmospheric chemistry of the oxygenates, their major oxidation products, and their influence on ozone and other trace gases within the troposhere.
Author: Walter Klöpffer
Publisher: John Wiley & Sons
ISBN: 3527611622
Category : Science
Languages : en
Pages : 258
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Book Description
This compilation on the degradation of 1,100 commercially important chemical products is the first publication to make this knowledge publicly accessible in one book. The data and annotations have been painstakingly assembled over a 10-year period in a collaboration between academia and regulatory authorities. The work explains in detail the methods, including computational ones, for the environmental assessment of volatile and semi-volatile substances, and is rounded off with data tables of degradation rates. A key resource for manufacturers and regulators of such substances.
Author: Heidi Lynn Bethel
Publisher:
ISBN:
Category : Hydroxyl group
Languages : en
Pages : 414
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Author: Emmanuel Assaf
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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The hydroxyl radical OH and hydroperoxy radical HO2 radicals are key species in many oxidation processes in the atmosphere. The degradation of volatile organic compounds under tropospheric conditions is induced by reactions with hydroxyl radicals followed by the subsequent chemistry of the initial OH oxidation products with O2. This thesis was focused on the kinetic study of some of these atmospherically relevant reactions to better understand their oxidation mechanisms using an experimental system of laser photolysis coupled to Laser Induced Fluorescence (LIF, for OH radical) and continuous-wave Cavity Ring-Down Spectroscopy (cw-CRDS, for OH, HO2 and RO2 radicals) detection techniques. After determining the infrared spectrum of OH, HO2 and CH3O2 radicals in the near infrared region and the absorption cross-sections of few selected lines, four systems were studied with the above mentioned techniques: CH3O2 + OH, C2H5O2 + OH, C3H7O2 + OH and C4H9O2 + OH. The rate constant and the HO2 yield of the four reactions were determined. In addition, the rate constants of few secondary reactions such as CH3O + HO2, CH3O + CH3O or OH + HO2 have been determined.
Author: Barbara J. Finlayson-Pitts
Publisher: Elsevier
ISBN: 0080529070
Category : Science
Languages : en
Pages : 993
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Book Description
Here is the most comprehensive and up-to-date treatment of one of the hottest areas of chemical research. The treatment of fundamental kinetics and photochemistry will be highly useful to chemistry students and their instructors at the graduate level, as well as postdoctoral fellows entering this new, exciting, and well-funded field with a Ph.D. in a related discipline (e.g., analytical, organic, or physical chemistry, chemical physics, etc.). Chemistry of the Upper and Lower Atmosphere provides postgraduate researchers and teachers with a uniquely detailed, comprehensive, and authoritative resource. The text bridges the "gap" between the fundamental chemistry of the earth's atmosphere and "real world" examples of its application to the development of sound scientific risk assessments and associated risk management control strategies for both tropospheric and stratospheric pollutants. - Serves as a graduate textbook and "must have" reference for all atmospheric scientists - Provides more than 5000 references to the literature through the end of 1998 - Presents tables of new actinic flux data for the troposphere and stratospher (0-40km) - Summarizes kinetic and photochemical date for the troposphere and stratosphere - Features problems at the end of most chapters to enhance the book's use in teaching - Includes applications of the OZIPR box model with comprehensive chemistry for student use
Author: Sui So
Publisher:
ISBN:
Category : Atmospheric chemistry
Languages : en
Pages : 346
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[Beta]-Hydroxyperoxyl radicals are formed during atmospheric oxidation of unsaturated volatile organic compounds (VOCs) such as isoprene. They are also important intermediates in the combustion of alcohols. In these environments the unimolecular isomerisation and decomposition of [beta]-hydroxyperoxyl radicals may be of importance. Results of ion-trap mass spectrometry generating a prototypical distonic charge-tagged [beta]-hydroxyalkyl radical anion •CH2C(OH)(CH3)CH2C(O)O- have been obtained by a collaborating research group. The subsequent reaction of the radical anion with O2 in the gas phase has been investigated under conditions that are devoid of complicating radical-radical reactions. In this thesis, quantum chemical calculations and master equation/RRKM theory modelling are used to rationalise the results and discern a reaction mechanism. Reaction is found to proceed via initial hydrogen abstraction from the [gamma]-methylene group and [beta]-hydroxyl group, with both reaction channels eventually forming isobaric product ions due to loss of either •OH + HCHO or •OH + CO2. Isotope labelling studies confirm that a 1,5-hydrogen shift from the [beta]-hydroxyl functionality results in a hydroperoxyalkoxyl radical intermediate that can undergo further unimolecular dissociation. Furthermore, facile decomposition of [beta]-hydroxyperoxyl radicals has been confirmed to yield •OH in the gas phase. Moreover, the influence of an anionic charge on the reaction chemistry of [beta]-hydroxyperoxyl radicals has been investigated by examining the molecular orbitals of a distonic [beta]-hydroxyperoxyl radical anion analogue •OOCH2CH(OH)CH2C(O)O-. Instead of following the conventional Aufbau principle, the radical anion exhibits a peculiar electronic arrangement, where the singly occupied molecular orbital (SOMO) is no longer the frontier orbital and carries energy lower than other doubly occupied molecular orbitals (HOMOs). This phenomenon is manifested as SOMO-HOMO conversion and is caused by the through space stabilisation between the interaction of the anion and radical site. Further investigation of the other C4H6O5•- isomers involved in the unimolecular reaction mechanisms of the hydroxyperoxyl radical anion •OOCH2CH(OH)CH2C(O)O- revealed that these radical anion isomers exhibit different extent of orbital conversion. As a result, the reaction chemistry of this radical anion is influenced by various additional stabilities associated with the unconventional electron arrangement, switching the dominant reaction pathway from [beta]-OH abstraction in the relevant neutral radical to C-H abstraction at the [beta]-carbon in the radical anion analogue. Despite the change in product distribution, all reaction pathways remain the same in both the neutral radical and radical anion analogues. Enols are emerging as trace atmospheric components that may play a significant role in the formation of organic acids in the atmosphere. They are unsaturated VOCs and their oxidation involves hydroxyperoxyl radicals as key intermediates. It has recently been discovered that acetaldehyde can undergo UV-induced isomerisation to vinyl alcohol (the enol counterparts) under atmospheric conditions. The •OH-initiated oxidation chemistry of vinyl alcohol has been investigated in this thesis, using quantum chemical calculations and energy-grained master equation simulations. The reaction proceeds by •OH addition at both the [alpha]-carbon (66%) and [beta]-carbon (33%) of the [pi] system, yielding the C-centred radicals •CH2CH(OH)2 and HOCH2C•HOH respectively. Subsequent trapping by O2 leads to the respective peroxyl radicals. About 90% of the chemically activated population of the major peroxyl radical adduct •O2CH2CH(OH)2 is predicted to undergo fragmentation to produce formic acid and formaldehyde, with regeneration of •OH. The minor peroxyl radical CH2(OH)CH(OH)O2• is even less stable and almost exclusively undergoes HO2• elimination to form glycolaldehyde. The •OH-initiated oxidation of vinyl alcohol ultimately leads to three main product channels, being (i) •O2CH2CH(OH)2 (8%), (ii) HC(O)OH + HCHO + •OH (56%) and (iii) HOCH2CHO + HO2• (37%). This study supports previous findings that vinyl alcohol should be rapidly removed from the atmosphere by reaction with •OH and O2, with glycolaldehyde being identified as a previously unconsidered product. Moreover, it is also shown that direct chemically activated reactions can lead to •OH and HO2• (HOx) recycling. Following the study on the acetaldehyde-vinyl alcohol pair, the photo-isomerisation of glycolaldehyde to 1,2-ethenediol has been studied. The keto-enol isomerisation is associated with a barrier of 66 kcal mol-1 and involves a double hydrogen shift mechanism to give the lower energy Z isomer. This barrier lies below the energy of the UV/Vis absorption band of glycolaldehyde and is also considerably below the energy of the products resulting from photolytic decomposition. The atmospheric oxidation of 1,2-ethenediol by •OH is initiated by radical addition to the [pi] system to give the •CH(OH)CH(OH)2 radical, which is subsequently trapped by O2 to form the peroxyl radical •O2CH(OH)CH(OH)2. According to kinetic simulations, collisional deactivation of the latter is negligible and cannot compete with rapid fragmentation reactions, which lead to (i) formation of glyoxal hydrate and HO2• through an [alpha]-hydroxyl mechanism (96%) and (ii) two molecules of formic acid with release of •OH through a [beta]-hydroxyl pathway (4%). The lifetime of the two enols in the presence of tropospheric levels of •OH is determined to be around 4 hours and 68 hours respectively. Phenomenological rate coefficients for these two oxidation reactions are obtained for use in atmospheric chemical modelling. Finally, photo-induced dissociation and isomerisation of other common tropospheric carbonyl compounds, namely methyl vinyl ketone (MVK) and methacrolein (MACR), has been reinvestigated. The reaction of both molecules proceeds through dissociation, cyclisation and hydrogen shift (including keto-enol isomerisation) pathways. From the simulation of reaction dynamics, MACR photolysis is significantly less efficient than MVK photolysis, which is consistent with the experimental data in the literature. Isomerisation dominates dissociation in the actinic spectrum at longer wavelengths for both MVK and MACR photolysis. The total photolysis rate of MVK and MACR is calculated to be 3.8 x 10-5 s-1 and 8.6 x 10-7 s-1 respectively. The study reveals that MVK and MACR photolysis may lead to formation of new atmospheric VOCs such as hydroxylbutadiene from MVK and dimethylketene from MACR.
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Languages : en
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