Reaction Of Ground State Oxygen Atoms Research Articles

Analysis of Nascent Rotational Energy Distributions and Reaction Mechanisms of the Gas-Phase Radical-Radical Reaction O(3P)+(CH3)2CH→C3H6+OH

This paper reports on the gas-phase radical-radical dynamics of the reaction of ground-state atomic oxygen [O((3)P), from the photodissociation of NO(2)] with secondary isopropyl radicals [(CH(3))(2)CH, from the supersonic flash pyrolysis of isopropyl bromide]. The major reaction channel, O((3)P)+(CH(3))(2)CH→C(3)H(6) (propene)+OH, is examined by high-resolution laser-induced fluorescence spectroscopy in crossed-beam configuration. Population analysis shows bimodal nascent rotational distributions of OH (X(2)Π) products with low- and high-N'' components in a ratio of 1.25:1. No significant spin-orbit or Λ-doublet propensities are exhibited in the ground vibrational state. Ab initio computations at the CBS-QB3 theory level and comparison with prior theory show that the statistical method is not suitable for describing the main reaction channel at the molecular level. Two competing mechanisms are predicted to exist on the lowest doublet potential-energy surface: direct abstraction, giving the dominant low-N'' components, and formation of short-lived addition complexes that result in hot rotational distributions, giving the high-N'' components. The observed competing mechanisms contrast with previous bulk kinetic experiments conducted in a fast-flow system with photoionization mass spectrometry, which suggested a single abstraction pathway. In addition, comparison of the reactions of O((3)P) with primary and tertiary hydrocarbon radicals allows molecular-level discussion of the reactivity and mechanism of the title reaction.

Quantum chemical investigation of the reaction of O(3 P 2) with certain hydrocarbon radicals

The reaction of ground-state atomic oxygen [O(3 P 2)] with methyl, ethyl, n-propyl and isopropyl radicals has been studied using the density functional method and the complete basis set model. The energies of the reactants, products, reaction intermediates and various transition states as well as the reaction enthalpies have been computed. The possible product channels and the reaction pathways are identified in each case. In the case of methyl radical the minimum energy reaction pathway leads to the products CO + H2 + H. In the case of ethyl radical the most facile pathway leads to the products, methanal + CH3 radical. For propyl radical (n- and iso-), the minimum energy reaction pathways would lead to the channel containing ethanal + methyl radical.

Kinetics of the Reactions of O(3P) with CCl2CH2, (Z)-CHClCHCl, and CCl2CCl2: A Temperature Dependence Study

Absolute rate coefficients for the gas-phase reactions of ground-state oxygen atoms with CCl(2)=CH(2) (1), (Z)-CHCl=CHCl (2) and CCl(2)=CCl(2) (3) have been measured directly using the fast flow discharge technique. The experiments were carried out under pseudo-first-order conditions with [O((3)P)](0) << [chloroethene](0). The temperature dependences of the reactions of O((3)P) with CCl(2)=CH(2), (Z)-CHCl=CHCl and CCl(2)=CCl(2) were studied in the range 298-359 K. The kinetic data obtained were used to derive the following Arrhenius expressions (in units of cm(3) molecule(-1) s(-1)): k(1) = (1.82 +/- 1.29) x 10(-11) exp[-(12.63 +/- 0.97) x 10(3)/RT], k(2) = (1.56 +/- 0.92) x 10(-11) exp[-(16.68 +/- 1.54) x 10(3)/RT], k(3) = (4.63 +/- 1.38) x 10(-11) exp[-(19.59 +/- 3.21) x 10(3)/RT]. This is the first temperature dependence study of the reactions of O((3)P) atoms with (Z)-CHCl=CHCl and CCl(2)=CCl(2). All the rate coefficients display a positive temperature dependence and pressure independence, which points to the importance of the irreversibility of the addition mechanism for these reactions. The obtained rate coefficients are compared with previous studies carried out mainly at room temperature. The rates of addition of O atoms and OH radicals to the double bond of alkenes at 298 K are related by the expression: log k(OH) = 0.57278 log k(O(3P)) - 4.095. A correlation is presented between the reactivity of chloroethenes toward O atoms and the second-order perturbational term of the frontier molecular orbital theory which carries the contribution of the different atomic orbitals to the HOMO of the chloroethene. To a first approximation, this correlation allows room-temperature rate coefficients to be predicted within +/-25-30% of the measured values.

Ab initio investigations of the radical-radical reaction of O(P3)+C3H3

We present ab initio calculations of the reaction of ground-state atomic oxygen [O(P3)] with a propargyl (C3H3) radical based on the application of the density-functional method and the complete basis-set model. It has been predicted that the barrierless addition of O(P3) to C3H3 on the lowest doublet potential-energy surface produces several energy-rich intermediates, which undergo subsequent isomerization and decomposition steps to generate various exothermic reaction products: C2H3+CO, C3H2O+H, C3H2+OH, C2H2+CHO, C2H2O+CH, C2HO+CH2, and CH2O+C2H. The respective reaction pathways are examined extensively with the aid of statistical Rice-Ramsperger-Kassel-Marcus calculations, suggesting that the primary reaction channel is the formation of propynal (CHCCHO)+H. For the minor C3H2+OH channel, which has been reported in recent gas-phase crossed-beam experiments [H. Lee et al., J. Chem. Phys. 119, 9337 (2003); 120, 2215 (2004)], a comparison on the basis of prior statistical calculations is made with the nascent rotational state distributions of the OH products to elucidate the mechanistic and dynamic characteristics at the molecular level.

Laboratory Studies on the Formation of Ozone (O3) on Icy Satellites and on Interstellar and Cometary Ices

The formation of ozone (O3) in neat oxygen ices was investigated experimentally in a surface-scattering machine. At 11 K, solid oxygen was irradiated with energetic electrons; the chemical modification of the target was followed on-line and in situ via Fourier transform infrared spectroscopy (FTIR; solid state) and quadrupole mass spectrometry (QMS; gas phase). The dominant product identified was the ozone molecule in the bent, C2v symmetric structure, O3(X 1A1); the cyclic D3h isomer was not observed. The associated van der Waals complexes [O3...O] and [O3...O3] could also be detected via infrared spectroscopy, verifying explicitly the existence of oxygen atoms in the matrix at 11 K. Three different formation mechanisms of ozone were revealed. Two pathways involve the reaction of suprathermal oxygen atoms with molecular oxygen [O2(X 3Σ)] at 11 K. Once the sample was warmed after the irradiation to about 38 K, a third, thermal reaction pathway involving the barrierless reaction of ground-state oxygen atoms with molecular oxygen sets in. During the warm-up phase, the inherent sublimation of oxygen and ozone was monitored by mass spectrometry and occurs in the ranges 28-43 and 58-73 K, respectively. Our data are of help to understand the mechanisms of ozone formation within apolar interstellar and cometary ices and could also be applicable to outer solar system icy bodies, such as the moons of Jupiter (Ganymede, Europa, and Callisto) and Saturn (Rhea and Dione), where ozone and/or condensed oxygen has been observed.

A theoretical study of the reaction of O(3P) with an allyl radical C3H5

Ab initio calculations of the reaction of ground-state atomic oxygen [O(3P)] with an allyl radical (C3H5) have been carried out using the density functional method and the complete basis set model. On the calculated lowest doublet potential energy surface, the barrierless association of O(3P) to C3H5 forms three energy-rich addition intermediates, which are predicted to undergo subsequent isomerization and decomposition steps leading to various products: C3H4O+H, CH2O+C2H3, C2H4+CHO, C2H2O+CH3, C2H5+CO, C3H4+OH, and C2H4O+CH. The respective reaction mechanisms through the three addition intermediates are presented, and it has been found that the barrier height, reaction enthalpy, and the number of intermediates involved along the reaction coordinate are of extreme importance in understanding such reactive scattering processes. With the aid of Rice–Ramsperger–Kassel–Marcus calculations, the major reaction pathway is predicted to be the formation of acrolein (C3H4O)+H, which is consistent with the previous gas-phase bulk kinetic experiment performed by Gutman et al. [J. Phys. Chem. 94, 3652 (1990)]. For the minor C3H4+OH channel, which has been newly found in the recent crossed beam investigations, a second barrierless, direct H-atom abstraction from the central carbon of C3H5 is calculated to compete with the addition process due to the little C–H bond dissociation energy and the formation of a stable allene product. The dynamic and kinetic characteristics of the reaction mechanism are discussed on the basis of the comparison of prior statistical calculations to the nascent internal distributions of the observed OH product.

Crossed beam investigations of the reaction dynamics of O(3P) with allyl radical, C3H5

The reaction of ground-state atomic oxygen (O(3P)) with allyl radical (C3H5) was investigated in the crossed beam configuration. O(3P) and C3H5 were generated by the photodissociation of NO2 and the supersonic flash pyrolysis of allyl iodide, respectively. The nascent internal distributions of the OH(X2Π : v″=0,1) reaction product from the newly observed channel of O(3P)+C3H5→C3H4+OH were probed by laser induced fluorescence (LIF) spectroscopy. The distributions showed significant excitations with an unusual bimodal feature: the low and high rotational components without spin-orbit and Λ-doublet propensities in the ground and first excited vibrational states. On the basis of population analysis and comparison with the ab initio and statistical calculations, the experimental distributions are estimated to be totally non-statistical and suggest that the dynamics of the reaction might be described by two competing mechanisms: a major direct abstraction process and an indirect short-lived addition-complex forming process.

Theoretical study of the homologous reactions of ground-state oxygen atoms with Br2 and BrCI molecules

La methode des trajectoires quasi- classiques est employee a l'etude du mecanisme des reactions homologues entre des atomes d'oxygene et des molecules de Br 2 et de BrCl, O+Br 2 → OBr+Br et O+BrCl → OBr+Cl. La dependance de la dynamique de ces reactions a egalement ete etudiee en fonction de leur energie cinetique relative initiale. Les resultats obtenus suggerent que la reactivite plus elevee du systeme O+BrCl, observee experimentalement, qui contrairement a ce qui est attendu compte du potentiel d'ionisation tenu plus eleve de BrCl, est compatiblde avec la dynamique de type complexe de cette reaction. Cet argument est conforte par l'application de la theorie RRKM-AM qui decrit de facon satisfaisante la reaction O+BrCl et non pas la reaction O+Br 2 . La variation des sections efficaces reactives, des distributions angulaires et de l'energie de translation des porduits en fonction de l'energie initiale de collision est examinee et les differences importantes sont soulignees

Comparison of the Kinetics of O(3P) Reactions with the Four Butenes over Wide Temperature Ranges

Rate coefficients for reactions of ground-state oxygen atoms with isobutene, trans-2-butene, and cis-2-butene have been measured using the high-temperature photochemistry (HTP) technique. The oxygen atoms were generated by flash photolysis of either O[sub 2] or CO[sub 2] and the relative atom concentrations were monitored by resonance fluorescence. We find, in cm[sup 3] molecule[sup [minus]1] s[sup [minus]1] units, for isobutene, k(284-1015 K) = 2.0 x 10[sup [minus]15](T/K)[sup 1.28] exp(543 K/T); trans-2-butene, k(292-1022 K) = 3.9 x 10[sup [minus]17](T/K)[sup 1.87] exp(743 K/T); and cis-2-butene, k(292-1086 K) = 2.4 x 10[sup [minus]17](T/K)[sup 1.94] exp(716 K/T). The 2[sigma] precision limits are around [+-]10%, and the corresponding 2[sigma] accuracy limits are estimated to be about [+-]25%. Conventional transition-state-theory calculations for the electrophilic O-addition to the double bond yield at high temperatures rate coefficients smaller than observed. A method is developed for estimating rate coefficients for H abstraction. When the results are added to those of the addition, good agreement with experiments is attained. The differences between the k(T) expressions for the present three reactions and the corresponding 1-butene reaction are discussed. Based on these observations, a method is presented for estimating rate coefficients for O-atom reactions with higher olefins over wide temperature ranges. 38 refs.,more » 8 figs., 4 tabs.« less

Infrared chemiluminescence from the O + CF2reaction: part 1.—Kinetics of the emission near 2000 cm–1

Time-resolved infrared chemiluminescence has been observed from the reaction of ground-state oxygen atoms with CF2(X1A1) radicals. FTIR measurements were first used to establish the time dependence of the emission spectrum, and kinetic measurements were then carried out using a series of narrowband IR filters. IR emission observed between 1840 and 2350 cm–1 was assigned to CO2 formed in the reaction sequence O + CF2→ FCO + F, O + FCO → CO2+ F and emitting in the Δv3=–1 bands. Total IR emission intensities were correlated with CF2 concentrations as measured by laser-induced fluorescence. Changes in the kinetics and intensities of the IR emission as a function of wavenumber and reagent pressures were consistent with this formation scheme followed by quenching of vibrationally excited CO2, mainly by collisions with O atoms. An upper limit of 0.06 was estimated for the ratio of vibrationally excited CO to CO2 produced in the system.

Direct rate constant measurements for the reaction of ground-state atomic oxygen with ethylene, 244-1052K

The rate constant for the reaction of ground-state atomic oxygen with ethylene was determined by using two techniques: flash photolysis-resonance fluorescence (FP-RF, 244-1052 K) and discharge flow-resonance fluorescence (DF-RF, 298-1017 K). Kinetic complications due to the presence of molecular oxygen in the FP-RF experiments at high temperatures (T > 800 K) were overcome by using NO as the photolytic source of the O atoms. The rate constant, k/sub 1/ (T), derived in this study exhibits extreme non-Arrhenius behavior, but it can be successfully fit to the sum of exponentials expression, 244-1052 K, k/sub 1/(T) = (1.02 +/- 0.06) x 10/sup -11/ exp(-753 +/- 17 K/T) + (2.75 +/- 0.26) x 10/sup -10/ exp(-4220 +/- 550 K/T), in units of cm/sup 3/ molecule/sup -1/ s/sup -1/. Additionally, a fit of the results of this work to a simple transition-state theory expression and the comparison of these results with those of other workers are discussed.

Predicted rate constants for the exothermic reactions of ground state oxygen atoms and CH radicals

A potential function has been derived for the ground-state surface of HCO which reproduces the spectroscopic properties of the equilibrium molecule and the results of ab-initio calculations at other stationary points on the surface. The potential has been used for a classical trajectory study of the vibrational excitation of CO on collision with fast H atoms and for a study of the reaction of ground-state oxygen atoms and CH radicals.

Branching ratio for the hydrogen atom product channel in the reaction of ground-state atomic oxygen with ethylene

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBranching ratio for the hydrogen atom product channel in the reaction of ground-state atomic oxygen with ethyleneJohn F. Smalley, Fred L. Nesbitt, and R. Bruce KlemmCite this: J. Phys. Chem. 1986, 90, 3, 491–497Publication Date (Print):January 1, 1986Publication History Published online1 May 2002Published inissue 1 January 1986https://doi.org/10.1021/j100275a028RIGHTS & PERMISSIONSArticle Views69Altmetric-Citations35LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (854 KB) Get e-Alerts

The Arrhenius Parameters for the Reactions of O Atoms with Ethene and Five Fluoroethenes

Abstract The rate constants for the reactions of ground-state oxygen atoms with ethene and five fluoroethenes have been measured over the temperature range of 240–450 K, using a pulse radiolysis-resonance absorption technique. The rate constants were well expressed by the following Arrhenius expressions: k(O+C2H4)=8.4×106 exp(−712⁄T); k(O+C2H3F)=3.1×106 exp(−622⁄T); k(O+CH2=CF2)=2.4×106 exp(−638⁄T); k(O+cis-CHF=CHF)=1.9×106 exp(−500⁄T); k(O+C2HF3)=3.0×106 exp(−544⁄T); k(O+C2F4)=8.1×106 exp(−634⁄T), in units of m3mol−1 s−1. The change in the preexponential factors with the degree of fluorination is discussed in terms of the conventional transition-state theory.

ChemInform Abstract: RATE CONSTANTS FOR THE REACTION OF GROUND‐STATE OXYGEN ATOMS WITH METHANOL FROM 297 TO 544 K

Chemischer InformationsdienstVolume 13, Issue 35 Preparative Organic Chemistry ChemInform Abstract: RATE CONSTANTS FOR THE REACTION OF GROUND-STATE OXYGEN ATOMS WITH METHANOL FROM 297 TO 544 K R. L. FAILES, R. L. FAILESSearch for more papers by this authorD. L. SINGLETON, D. L. SINGLETONSearch for more papers by this authorG. PARASKEVOPOULOS, G. PARASKEVOPOULOSSearch for more papers by this authorR. S. IRWIN, R. S. IRWINSearch for more papers by this author R. L. FAILES, R. L. FAILESSearch for more papers by this authorD. L. SINGLETON, D. L. SINGLETONSearch for more papers by this authorG. PARASKEVOPOULOS, G. PARASKEVOPOULOSSearch for more papers by this authorR. S. IRWIN, R. S. IRWINSearch for more papers by this author First published: August 31, 1982 https://doi.org/10.1002/chin.198235135AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume13, Issue35August 31, 1982 RelatedInformation

Reaction of ground-state oxygen atoms with cis- and trans-1,2-difluoroethene

The reactions of ground-state oxygen atoms with cis- and trans-1,2-difluorethene have been studied over the pressure range 50–760 mmHg at room temperature. The results show that the primary reaction in both cases is almost entirely O + CHFCHF → CHFO + CHF. The monofluorocarbene radical formed adds stereospecifically to the difluoroethene, and the resulting hot 1,2,3-trifluorocyclopropane may be collisionally stabilised or isomerise to 1,2,3-trifluoropropenes.

Absolute Rate Constants for the Reactions of O(3P) with Several Molecules

Abstract Absolute rate constants were measured for several reactions of ground-state oxygen atoms at 296±2 K. The pulse-radiolysis of O2, CO, or CO2 in the He diluent was used to produce oxygen atoms, and the atomic concentration was monitored by the resonance absorption. The measurements were made in the pressure range from 50 to 950 Torr (1 Torr \simeq133.3 Pa). The rate constants thus obtained were (2.5±0.3)×10−34 for O+O2+He and (1.0±0.2)×10−35 for O+CO+He in units of cm6 molecule−2 s−1 (1 cm6 molecule−2 s−1\simeq3.626×1035 m6 mol−2 s−1). For simple olefins, the following bimolecular rate constants (k⁄10−12 cm3 molecule−1 s−1) were obtained: Ethylene (1.0±0.2), propene (4.7±0.3), 1-butene (4.7±0.5), trans-2-butene (23±3), cis-2-butene (20±3), 2-methylpropene (17±2), 2-methyl-2-butene (55±5), 1,3-butadiene (20±2), (1 cm3 molecule−1 s−1\simeq6.022×1017 m3 mol−1 s−1). These rate constants were in fair agreement with the literature values.

Dye laser flash photolysis kinetics study of the reaction of ground-state atomic oxygen with hydrogen peroxide

Dye laser flash photolysis kinetics study of the reaction of ground-state atomic oxygen with hydrogen peroxide

The kinetics and mechanism of the reaction of atomic oxygen with acetylene

A photoionization mass spectrometer has been used to study the reaction of ground-state oxygen atoms with acetylene. The oxygen atoms were produced in the absence of molecular oxygen in a discharge-flow system with nitrogen as the principal carrier gas. Several of the free radicals and stable product molecules that were observed previously have been studied in more detail. Experiments with added gases have shown that the methylene radicals observed are probably in their ground, triplet state. The ratio of rate constants for the reactions of CH 2 with O 2 and O respectively was found to be approximately 1:10. The dependence of the C 3 H 3 radical concentration on the experimental conditions showed that C 3 H 3 was formed in a secondary reaction, probably involving an excited molecule or radical. The rate constant for the reaction of the HCCO radical with O 2 was measured as 2.2 ± 1.2х10 7 1 mol -1 s -1 . The product observed at mass 42 appears to be ground-state ketene formed in the primary step, perhaps via a triplet state. However, the possibility that the ketene might be formed in a secondary process cannot be dismissed. The rate constant for the reaction of ground-state oxygen atoms with ketene was measured, with a result significantly lower than a previous study. The diacetylene concentration showed a complex dependence on reaction conditions. Analysis of the approach of [C 4 H 2 ] to its steady-state concentration gave a rate constant for the reaction of oxygen atoms with diacetylene of 1.6 ± 0.5 х10 9 1 mol -1 s -1 . The relation of these results to previous studies is discussed briefly. It is suggested that a reaction of one or more of the energetic primary products, such as electronically excited CH 2 , HCCO or ketene, could be responsible for the chemiluminescence of CH, OH and CHO.

Reaction of Oxygen Atoms, O(3P), with Ethylene in Liquid Nitrogen Solution

The reaction of ground-state oxygen atoms, O(3P), with ethylene and ethylene-d4 in liquid nitrogen solution at 77° K has been studied. The major and perhaps the exclusive products are ethylene oxide and acetaldehyde. The ratio of acetaldehyde to ethylene oxide is 1.2 ± 0.1 for ethylene and 0.91 ± 0.09 for ethylene-d4. Much smaller amounts of formaldehyde and trace quantities of cyclopropane are also observed.The effect of the concentration of ethylene on the quantum yields of addition products was measured. A limiting quantum yield of oxygen atoms scavenged by ethylene to form the addition products was 0.12 + 0.01. The low quantum yield suggests an appreciable cage recombination of the ground-state oxygen atoms with the trace amounts of molecular oxygen present. The effect of the concentration of added oxygen on the product yields and the relative rate constant for the addition of O(3P) to molecular oxygen and to ethylene were determined. The ratio [Formula: see text] is 6.0 ± 1.0 and the relative rate constant for the addition of O(3P) to ethylene and to ethylene-d4, [Formula: see text], is 2.0 ± 0.1.The type of products formed and the isotope effects observed are discussed in terms of the mechanism of addition of O(3P) atoms to ethylene.