L. Nelson

Bio: L. Nelson is an academic researcher from University College Dublin. The author has contributed to research in topics: Reaction rate constant & Radiolysis. The author has an hindex of 6, co-authored 10 publications receiving 286 citations.

Absolute and relative rate constants for the reactions of hydroxyl radicals and chlorine atoms with a series of aliphatic alcohols and ethers at 298 K

Abstract: Rate constants for the gas-phase reactions of hydroxyl radicals and chlorine atoms with aliphatic alcohols and ethers have been determined at 298 ± 2 K and at a total pressure of 1 atmosphere. The OH radical rate data were obtained using both the absolute technique of pulse radiolysis combined with kinetic UV spectroscopy and a conventional photolytic relative rate method. The Cl atom rate constants were measured using only the relative rate method. Values of the rate constants in units of 10−12 cm3 molecule−1 s−1 are: The above relative rate constants are based on the values of (OH + c-C6H12) = 7.49 × 10−12 cm3 molecule−1 s−1 and (Cl + c-C6H12) = 311 × 10−12 cm3 molecule−1 s−1. Attempts to corre late the trends in the rate constant data in terms of the bond dissociation energies and inductive effects are discussed.

Kinetics and mechanism for the oxidation of 1,1,1‐trichloroethane

Abstract: The reaction mechanisms for oxidation of CH3CCl2 and CCl3CH2 radicals, formed in the atmospheric degradation of CH3CCl3 have been elucidated. The primary oxidation products from these radicals are CH3CClO and CCl3CHO, respectively. Absolute rate constants for the reaction of hydroxyl radicals with CH3CCl3 have been measured in 1 atm of Argon at 359, 376, and 402 K using pulse radiolysis combined with UV kinetic spectroscopy giving (OH + CH3CCl3) = (5.4 ± 3) 10−12 exp(−3570 ± 890/RT) cm3 molecule−1 s−1. A value of this rate constant of 1.3 × 10−14 cm3 molecule−1 s−1 at 298 K was calculated using this Arrhenius expression. A relative rate technique was utilized to provide rate data for the OH + CH3 CCl3 reaction as well as the reaction of OH with the primary oxidation products. Values of the relative rate constants at 298 K are: (OH + CH3CCl3) = (1.09 ± 0.35) × 10−14, (OH + CH3CClO) = (0.91 ± 0.32) × 10−14, (OH + CCl3CHO) = (178 ± 31) × 10−14, (OH + CCl2O) < 0.1 × 10−14; all in units of cm3 molecule−1 s−1. The effect of chlorine substitution on the reactivity of organic compounds towards OH radicals is discussed.

Rate constants for the reactions of OH radicals and Cl atoms with diethyl sulfide, Di‐n‐propyl sulfide, and Di‐n‐butyl sulfide

Abstract: Rate constants for the reactions of OH radicals and Cl atoms with diethyl sulfide (DES), di-n-propyl sulfide (DPS), and di-n-butyl sulfide (DBS) have been determined at 295 ± 3 K and a total pressure of 1 atm. Hydroxyl radical rate data was obtained using the absolute technique of pulse radiolysis combined with kinetic spectroscopy. The chlorine atom rate constants were measured using a conventional photolytic relative rate method. The rate constant for the reaction of Cl atoms with dimethyl sulfide (DMS) was also determined. The following rate constants were obtained : k(OH+DES)=(11.6±2)×10 −12 cm 3 molecule −1 s −1 ; k(OH+DPS)=(21.5±3)×10 −12 cm 3 molecule −1 s −1 ; k(OH+DBS)=(37.4±5)×10 −12 cm 3 molecule −1 s −1 ; k(Cl+DMS)=(32.2±3)×10 −11 cm 3 molecule −1 s −1 ; k(Cl+DES)=(44.1±4)×10 −11 cm 3 molecule −1 s −1 ; k(Cl+DPS)=(51.8±4)×10 −11 cm 3 molecule −1 s −1 ; k(Cl+DBS)=(64.6±2)×10 −11 cm 3 molecule −1 s −1

An absolute and relative rate study of the reaction of oh radicals with dimethyl sulfide

Abstract: The gas phase reaction of OH radicals with dimethyl sulfide (CH3SCH3, DMS) has been studied using both an absolute and a relative technique at 295 ± 2 K and a total pressure of 1 atm. The absolute rate technique of pulse radiolysis combined with kinetic spectroscopy was applied. Using this technique a rate constant of (3.5 ± 0.2) × 10−12 cm3 molecule−1 s−1 was obtained. For the relative rate method, rate constants for the reaction of OH with DMS were found to increase with increasing concentrations of added NO. These results are compared with the large body of kinetic and mechanistic data previously reported in the literature.

Absolute and Relative Rate Constants for the Reactions of Hydroxyl Radicals and Chlorine Atoms with a Series of Aliphatic Alcohols and Ethers at 298 K

Abstract: Rate constants for the gas-phase reactions of hydroxyl radicals and chlorine atoms with aliphatic alcohols and ethers have been determined at 298 ± 2 K and at a total pressure of 1 atmosphere. The OH radical rate data were obtained using both the absolute technique of pulse radiolysis combined with kinetic UV spectroscopy and a conventional photolytic relative rate method. The Cl atom rate constants were measured using only the relative rate method. Values of the rate constants in units of 10−12 cm3 molecule−1 s−1 are: The above relative rate constants are based on the values of (OH + c-C6H12) = 7.49 × 10−12 cm3 molecule−1 s−1 and (Cl + c-C6H12) = 311 × 10−12 cm3 molecule−1 s−1. Attempts to corre late the trends in the rate constant data in terms of the bond dissociation energies and inductive effects are discussed.

Environmental Implications of Hydroxyl Radicals ((•)OH).

Abstract: The hydroxyl radical (•OH) is one of the most powerful oxidizing agents, able to react unselectively and instantaneously with the surrounding chemicals, including organic pollutants and inhibitors. The •OH radicals are omnipresent in the environment (natural waters, atmosphere, interstellar space, etc.), including biological systems where •OH has an important role in immunity metabolism. We provide an extensive view on the role of hydroxyl radical in different environmental compartments and in laboratory systems, with the aim of drawing more attention to this emerging issue. Further research on processes related to the hydroxyl radical chemistry in the environmental compartments is highly demanded. A comprehensive understanding of the sources and sinks of •OH radicals including their implications in the natural waters and in the atmosphere is of crucial importance, including the way irradiated chromophoric dissolved organic matter in surface waters yields •OH through the H2O2-independent pathway, and the ...

The reaction kinetics of dimethyl ether. I: High‐temperature pyrolysis and oxidation in flow reactors

Abstract: Dimethyl ether reaction kinetics at high temperature were studied in two different flow reactors under highly dilute conditions. Pyrolysis of dimethyl ether was studied in a variable-pressure flow reactor at 2.5 atm and 1118 K. Studies were also conducted in an atmospheric pressure flow reactor at about 1085 K. These experiments included trace-oxygen-assisted pyrolysis, as well as full oxidation experiments, with the equivalence ratio (ϕ) varying from 0.32 ≤ ϕ ≤ 3.4. On-line, continuous, extractive sampling in conjunction with Fourier Transform Infra-Red, Non-Dispersive Infra-Red (for CO and CO2) and electrochemical (for O2) analyses were performed to quantify species at specific locations along the axis of the turbulent flow reactors. Species concentrations were correlated against residence time in the reactor and species evolution profiles were compared to the predictions of a previously published detailed kinetic mechanism. Some changes were made to the model in order to improve agreement with the present experimental data. However, the revised model continues to reproduce previously reported high-temperature jet-stirred reactor and shock tube results. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet: 32: 713–740, 2000

Photooxidation of dimethyl sulfide and dimethyl disulfide. I: Mechanism development

Abstract: Detailed theoretical (Part I, this article) and experimental (Part II) investigations are presented for the mechanism of the atmospheric photooxidation of dimethyl sulfide (CH3SCH3) and dimethyl disulfide (CH3SSCH3). In this paper, comprehensive mechanisms for the atmospheric chemistry of CH3SCH3 and CH3SSCH3 are developed based on fundamental considerations of all available kinetic and mechanistic information.

A wide range modeling study of dimethyl ether oxidation

Abstract: A detailed chemical kinetic model has been used to study dimethyl ether (DME) oxidation over a wide range of conditions Experimental results obtained in a jet-stirred reactor (JSR) at I and 10 atm, 02 < 0 < 25, and 800 < T < 1300 K were modeled, in addition to those generated in a shock tube at 13 and 40 bar, 0 = 10 and 650 :5 T :5 1300 K The JSR results are particularly valuable as they include concentration profiles of reactants, intermediates and products pertinent to the oxidation of DME These data test the Idnetic model severely, as it must be able to predict the correct distribution and concentrations of intermediate and final products formed in the oxidation process Additionally, the shock tube results are very useful, as they were taken at low temperatures and at high pressures, and thus undergo negative temperature dependence (NTC) behavior This behavior is characteristic of the oxidation of saturated hydrocarbon fuels, (eg the primary reference fuels, n-heptane and iso- octane) under similar conditions The numerical model consists of 78 chemical species and 336 chemical reactions The thermodynamic properties of unknown species pertaining to DME oxidation were calculated using THERM

Wide range modeling study of dimethyl ether oxidation

Abstract: A detailed chemical kinetic model has been used to study dimethyl ether (DME) oxidation over a wide range of conditions. Experimental results obtained in a jet-stirred reactor (JSR) at I and 10 atm, 0.2 < 0 < 2.5, and 800 < T < 1300 K were modeled, in addition to those generated in a shock tube at 13 and 40 bar, 0 = 1.0 and 650 :5 T :5 1300 K. The JSR results are particularly valuable as they include concentration profiles of reactants, intermediates and products pertinent to the oxidation of DME. These data test the Idnetic model severely, as it must be able to predict the correct distribution and concentrations of intermediate and final products formed in the oxidation process. Additionally, the shock tube results are very useful, as they were taken at low temperatures and at high pressures, and thus undergo negative temperature dependence (NTC) behavior. This behavior is characteristic of the oxidation of saturated hydrocarbon fuels, (e.g. the primary reference fuels, n-heptane and iso- octane) under similar conditions. The numerical model consists of 78 chemical species and 336 chemical reactions. The thermodynamic properties of unknown species pertaining to DME oxidation were calculated using THERM.