- Pressure dependence and kinetic isotope effects in the absolute rate constant for methoxy radical reacting with NO2
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We have investigated the kinetics for the reaction CH3O ? + NO2 in N2 bath gas. The rate constants are well-fit by the Troe expression over the temperature (250-335 K) and pressure range (30-700 Torr) investigated. The termolecular rate constant is given by k1a0=4.29-0.37 +0.40×10-29T/298-(1.65±1.11) cm6 molecule-2 s-1, and the rate constant at the high-pressure limit is given by k1a∞=(1. 95±0.03)×10-11T/298-(1.13±0.18) cm3 molecule-1 s-1. We also studied the kinetics of the reaction of CD3O? + NO2 as a function of temperature and pressure under similar conditions as those for CH3O? + NO2. The resulting low- and high-pressure limiting rate constants are k2a0=9.97-0.91 +1.00×10-29T/298-(4.79±0.92) cm6 molecule-2 s-1 and k2a ∞=(1.91±0.02)×10-11T/298 -(1.11±0.09) cm3 molecule-1 s -1, respectively. The rate constants for the two isotopologues track each other closely as the high-pressure limit is approached. The present results agree with most previous results at 295 K over a range of pressures, but there is substantial disagreement about the temperature dependence.
- Chai, Jiajue,Dibble, Theodore S.
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Read Online
- Role of methyl nitrate in plasma exhaust treatment
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There is growing interest in the use of a nonthermal plasma combined with a catalyst for NOx removal from diesel engine exhaust streams, which contain excess oxygen (6-10%), low concentrations of hydrocarbons (100-1000 ppm), and significant concentrations of water (5-12%). Tests were performed to elucidate the effect of methyl nitrate (CH3ONO2) in the plasma-catalyst system since similar compounds have been proposed as reaction intermediates in NOx removal. NO, CO, CO2, O2, SO2, H2, Ar, C3H6, and C3H8 gases were mixed in N2 carrier. CH3ONO2 was prepared and added to the gas blend on test equipment simulating a diesel exhaust gas. CH3ONO2 was formed in a substantial yield on passing hydrocarbon/NOx/O2/N2 mixtures through a nonthermal plasma. The catalyst (consisted of two 24 mm x 24 mm long honeycombs) was very effective at removing CH3ONO2, which is converted into methanol and NO2. CH3ONO2 was not an important intermediate in the NOx removal reaction of the plasma-catalyst system.
- Hoard,Balmer,Wallington,Ball,Hurley,Wodzisz
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Read Online
- Investigation into the Pressure Dependence between 1 and 10 Torr of the Reactions of NO2 with CH3 and CH3O
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The kinetic and pressure dependence of the reactions of NO2 with CH3 and CH3O have been investigated in the gas phase at 298 K, at pressure from 1 to 10 Torr.A low-pressure discharge-flow laser-induced fluorescence (LIF) technique was used.In a consecutive process, CH3 reacted with NO2 to form CH3O, CH3 + NO2 --> CH3O + NO (1), which further reacted with NO2 to form products, CH3O + NO2 --> products (2).Reaction (1) displayed no discernible pressure dependence over the pressure range 1-7 Torr, and k1 was calculated to be (2.3 +/- 0.3)E-11 cm3 molecule-1 s-1.Reaction (2) displayed a strong pressure dependence and an RRKM analysis yielded the following limiting low- and high-pressure rate constants in He, k0 = 5.9E-29 cm6 molecule-2 s-1 and k = 2.1E-11 cm3 molecule-1 s-1.It is unrealistic to quote errors for this type of analysis.Parametrisation in the standard Troe form with Fc = 0.6 yielded k0 = (5.3 +/-)E-29 cm6 molecule-2 s-1 and k = (1.4 +/- 0.1)E-11 cm3 molecule-1 s-1.Atmospheric implications and possible reaction mechanisms are discussed.
- Biggs, Peter,Canosa-Mas, Carlos E.,Fracheboud, Jean-Marc,Parr, A. Douglas,Shallcross, Dudley E.,et al.
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- Fourier Transform Infrared Spectroscopic Study of the Thermal Stability of Peroxyacetyl Nitrate
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The unimolecular decomposition of peroxyacetyl nitrate (PAN) to form methyl nitrate and carbon dioxide has been studied over the temperature range 298-338 K by Fourier transform infrared spectroscopy (FTIR).Pure PAN samples (>98percent; 2-30 torr) were found to decompose thermally, nearly quantitatively, to these products, with the only other observed product being nitromethane (12)exp(-24.800+/-1800 cal/(K mol/RT)) s-1.Perdeuterio-PAN was synthesized and observed to decompose to perdeuteriomethyl nitrate and carbon dioxide with no apparent isotope effect.Experiments adding nitric oxide to the PAN are described which confirm the existence of two unimolecular pathways for the decomposition of peroxyacyl nitrates.One pathway is a concerted reaction most likely proceeding via a cyclic intermediate, and the other the previously identified equilibrium between PAN and the peroxyacetyl radical and nitrogen dioxide was determined to be 2.2*10-4 s-1 at 298 K.This rate is somewhat slower than previously reported for this pathway.The results are discussed with respect to the atmospheric liftime of PAN and the potential atmospheric production of methyl nitrate.
- Senum, G. I.,Fajer, R.,Gaffney, J. S.
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- Reaction of CH2OH with O2, NO, and NO2 at Room Temperature
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The reaction of CH2OH with O2, NO, and NO2 has been studied using pulse radiolysis to generate the radicals and ultraviolet absorption to observe the kinetics.Rate constant values of (0.88 +/- 0.02) x 10-11, (2.5 +/- 0.02) x 10-11, and (2.3 +/- 0.4) x 10-11 cm3 molecule-1 s-1 have been measured at room temperature and 1 atm pressure for the O2, NO, and NO2 reactions, respectively.Absorptions due to long-lived or stable products were observed in the same spectral region.A simple analysis of these observations suggests that formation of an adduct may dominate in the reaction of CH2OH with NO and NO2 but that this process accounts for only a minor route in the O2 reaction.
- Pagsberg, Palle,Munk, Jette,Anastasi, Christopher,Simpson, Victoria J.
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- Solid-State and Gas-Phase Structures and Energetic Properties of the Dangerous Methyl and Fluoromethyl Nitrates
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An improved synthesis of the simplest nitric acid ester, methyl nitrate, and a new synthesis of fluoromethyl nitrate use the metathesis of the corresponding iodomethanes with silver nitrate. Both compounds were identified by spectroscopy and the structures determined for in situ grown crystals by X-ray diffraction as well as in the gas phase by electron diffraction. Fluorination leads to structures with shorter C?O and N?O bonds, has an energetically destabilizing effect and increases friction sensitivity, but decreases detonation performance.
- Reichel, Marco,Krumm, Burkhard,Vishnevskiy, Yury V.,Blomeyer, Sebastian,Schwabedissen, Jan,Stammler, Hans-Georg,Karaghiosoff, Konstantin,Mitzel, Norbert W.
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supporting information
p. 18557 - 18561
(2019/11/19)
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- Cold-surface photochemistry of selected organic nitrates
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Reflection-absorption infrared (RAIR) spectroscopy has been used to explore the low temperature condensed-phase photochemistry of atmospherically relevant organic nitrates for the first time. Three alkyl nitrates, methyl, isopropyl, and isobutyl nitrate together with a peroxyacyl nitrate, peroxyacetyl nitrate (PAN), were examined. For the alkyl nitrates, similar photolysis products were observed whether they were deposited neat to the gold substrate or codeposited with water. In addition to peaks associated with the formation of an aldehyde/ketone and NO, a peak near 2230 cm-1 was found to emerge in the RAIR spectra upon UV photolysis of the thin films. Together with evidence obtained by thermal programmed desorption (TPD), the peak is attributed to the formation of nitrous oxide, N2O, generated as a product during the photolysis. On the basis of the known gas-phase photochemistry for the alkyl nitrates, an intermediate pathway involving the formation of nitroxyl (HNO) is proposed to lead to the observed N2O photoproduct. For peroxyacetyl nitrate, CO2 was observed as a predominant product upon photolytic decomposition. In addition, RAIR absorptions attributable to the formation of methyl nitrate were also found to appear upon photolysis. By analogy to the known gas-phase and matrix-isolated-phase photochemistry of PAN, the formation of methyl nitrate is shown to likely result from the combination of alkoxy radicals and nitrogen dioxide generated inside the thin films during photolysis.
- O'Sullivan, Daniel,McLaughlin, Ryan P.,Clemitshaw, Kevin C.,Sodeau, John R.
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p. 9890 - 9900
(2015/02/19)
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- S-alkylation of thiacalixarenes: A long-neglected possibility in the calixarene family
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Despite the high nucleophilicity of sulfur atoms, thiacalixarenes have been alkylated only on oxygen atoms thus far. Using strong alkylating agents (triflates, trialkyloxonium salts), the substitution of the sulfur bridges has been successfully accomplished. The corresponding sulfonium salts of thiacalix[4]arene are formed regio- and stereoselectively as a completely new type of substitution pattern in thiacalixarene chemistry. These compounds possess interesting conformational behavior and could be used as unusual alkylating agents with uncommon selectivity.
- Kundrat, Ondrej,Eigner, Vaclav,Dvorakova, Hana,Lhotak, Pavel
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supporting information; scheme or table
p. 4032 - 4035
(2011/09/20)
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- Vapor generation of inorganic anionic species after aqueous phase alkylation with trialkyloxonium tetrafluoroborates
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Aqueous phase reaction of trialkyloxonium tetrafluoroborates, R 3O+BF4- (R=Me, Et) has been tested in the alkylation of simple inorganic anionic substrates such as halogen ions, cyanide, thiocyanate, sulphide an
- D'Ulivo, Alessandro,Pagliano, Enea,Onor, Massimo,Pitzalis, Emanuela,Zamboni, Roberto
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experimental part
p. 6399 - 6406
(2010/04/06)
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- The atmospheric oxidation of diethyl ether: Chemistry of the C 2H5-O-CH(O?)CH3 radical between 218 and 335 K
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The products of the Cl atom initiated oxidation of diethyl ether (DEE) were investigated at atmospheric pressure over a range of temperatures (218-335 K) and O2 partial pressures (50-700 Torr), both in the presence and absence of NOx. The major products observed at 298 K and below were ethyl formate and ethyl acetate, which accounted for ≈60-80% of the reacted diethyl ether. In general, the yield of ethyl formate increased with increasing temperature, with decreasing O2 partial pressure, and upon addition of NO to the reaction mixtures. The product yield data show that thermal decomposition reaction (3), CH3CH2-O-CH(O ?)CH3 → CH3CH2-O-CH=O + CH3, and reaction (6) with O2, CH3CH 2-O-CH(O?)CH3 + O2 → CH3CH2-O-C(=O)CH3 + HO2 are competing fates of the CH3CH2-O-CH(O?) CH3 radical, with a best estimate of k3/k6 ≈ 6.9 × 1024 exp(-3130/T). Thermal decomposition via C-H or C-O bond cleavage are at most minor contributors to the CH3CH 2-O-CH(O?)CH3 chemistry. The data also show that the CH3CH2-O-CH(O?)CH 3 radical is subject to a chemical activation effect. When produced from the exothermic reaction of the CH3CH2-O-CH(OO ?)CH3 radical with NO, prompt decomposition via both CH3- and probably H-elimination occur, with yields of about 40% and ≤15%, respectively. Finally, at temperatures slightly above ambient, evidence for a change in mechanism in the absence of NOx, possibly due to chemistry involving the peroxy radical CH3CH2-O-CH(OO ?)CH3, is presented. the Owner Societies.
- Orlando, John J.
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p. 4189 - 4199
(2008/09/19)
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- Rate constants of the gas-phase reactions of CH3OOH with O3 and NOx at 293 K
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Using the long-path technique of Fourier transform infrared (LP FTIR) spectrometry, the rate coefficients of methyl hydroperoxide (MHP, CH3OOH) reactions with O3, NO2 and NO at (293 ± 2) K have been determined. The coefficients are kMHP + O3 = (7.3 ± 0.1) × 10 - 21, kMHP + NO2 = (9.6 ± 1.3) × 10- 21 and kMHP+NO -22 cm3 molecule-1 s-1. Random errors are ±2σ. The atmospheric lifetimes of MHP with respect to reactions with O3 and NO2 were estimated at 3.5 and 2.6 years, respectively. Finally, the results are discussed within the context of the atmospheric decay chemistry of MHP and its environmental impact.
- Chen, Zhongming,Wang, Caixia
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p. 233 - 238
(2007/10/03)
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- FTIR spectroscopic study of the OH-induced oxidation of two linear acetates: Ethyl and n-propyl acetates
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OH-induced oxidation mechanisms of ethyl and n-propyl acetates have been investigated at room temperature (298 ± 5 K) and atmospheric pressure by photolysing CH3ONO/acetate/NO mixtures with FTIR spectroscopy as analytical device. The main oxidation products and their yields were as follows: from ethyl acetate, acetic acid (0.75 ± 0.13), acetoxyacetaldehyde (0.15 ± 0.05), acetic anhydride (0.02 ± 0.01), formic acetic anhydride (0.02 ± 0.01) and peroxyacetyl nitrate (PAN); from n-propyl acetate, acetoxyacetaldehyde (0.22 ± 0.06), formic acetic anhydride (0.28 ± 0.03), acetic acid (0.15 ± 0.02), acetaldehyde (0.35 ± 0.10), peroxypropionyl nitrate (PPN) and probably acetoxypropionaldehyde (0.30 ± 0.10). From these data, oxidation schemes of these two acetates were elucidated. This study reveals in particular the specifc reactivity of acetates by confirming the novel α-ester rearrangement proposed recently by Tuazon et al. (J. Phys. Chem. A, 1998, 102, 2316) and then by showing that oxygenated alkoxyl radicals may not follow the same rules of reactivity as other alkoxyl radicals. This last observation shows the necessity for further experiments to understand the influence of the oxygenated function on alkoxyl reactivity.
- Picquet-Varrault,Doussin,Durand-Jolibois,Carlier
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p. 2595 - 2606
(2007/10/03)
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- Kinetic studies of the reactions CH3+NO2→products, CH3O+NO2→products, and OH+CH3C(O)CH3→CH3C(O)OH+CH3, over a range of temperature and pressure
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The title reactions were investigated using pulsed laser photolysis combined with pulsed laser induced fluorescence detection of CH3O to determine the rate coefficients for CH3+NO2→products (3) and CH3O+NO2→products (5) as a function of temperature and pressure, and to estimate the yield of CH3 (and thus the yield of CH3C(O)OH) from the reaction of OH with CH3C(O)CH3 (2) at two different temperatures. Reaction 3 has both bimolecular and termolecular components: a simplified falloff parametrization with Fcent = 0.6 gives k3b0 = (3.2±1.3)×10-28(T/297)-0.3 cm6 s-1 and k3b∞ = (4.3±0.4)×10-11(T/297)-1.2 cm3 s-1 with CH3NO2 the likely product. The rate constant for the bimolecular reaction pathway to form CH3O+NO (3a) was found to be 1.9×10-11 cm-3 s-1. The low- and high-pressure limiting rate coefficients for reaction between CH3O and NO2 to form CH3ONO2 (5b) were derived as k5b0 = (5.3±0.3)×10-29(T/297)-4.4 cm6 s-1 and k5b∞ = (1.9±0.05)×10-11(T/297)-1.9 cm3 s-1, respectively. Although the final result is associated with some experimental uncertainty, we find that CH3 is formed in the reaction between OH and CH3C(O)CH3 at ≈50% yield at room temperature and 30% at 233 K.
- Wollenhaupt, Matthias,Crowley, John N.
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p. 6429 - 6438
(2007/10/03)
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- Mechanism of the primary stages of decomposition of aliphatic nitro- and fluoronitronitramines
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The primary stage of the decomposition of compounds RN(NO2)CH2C(NO2)2X is the homolytic cleavage of the C - NO2 bond, at X = NO2 and N - NO2 bond at X = F. The inductive effect of substituents decreases the dissociation energies of the C - N and N - N bonds by 1-2 kcal mol-1. Kinetic effects caused by the spatial interaction of groups and by stepwise decomposition of polyfunctional compounds are described.
- Korsounskii,Matveev,Nazina,Nazin
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p. 253 - 258
(2007/10/03)
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- Ferroelectric liquid crystals for nonlinear optics applications
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The present invention provides ferroelectric liquid crystal and liquid crystal compounds, among which are compounds which possess large X(2), i.e. second order nonlinear susceptibility and thus make them useful in optical and nonlinear optical applications. The invention includes chiral nonracemic compounds of formula STR1 where one of n or m is 1; k is 1 and B is COO or OOC; R' is a straight-chain or branched alkyl or monoalkene group having from 1 to 20 carbon atoms where one or more of the non-neighboring carbon atoms in R', except any unsaturated carbon atoms, can be replaced with O, S or a Si(CH3)2 group; and R' is a chiral nonracemic tail group selected from the group consisting of --O--C*H(CH3)Rc, --O--C*H(CH3)COORd and --O--CH2 C*HF--C*HF--R6 in which the * indicates an asymmetric carbon enriched in one stereoconfiguration which for --O--CH2 C*HF--C*HF--Re is either the (S,S) or (R,R) stereoconfiguration wherein: Rc is a straight-chain or branched alkyl or monoalkene group having 2 to 15 carbon atoms; Rd is a straight-chain or branched alkyl or monoalkene group having 2 to 13 carbon atoms and Re is a straight-chain or branched alkyl or monoalkene group having 2 to 11 carbon atoms wherein in Rc, Rd or Re one or more non-neighboring carbon atoms, except any unsaturated carbon atoms, can be substituted with an O, S, or Si(CH2)2 group.
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- Atmospheric chemistry of Di-tert-Butyl ether: Rates and products of the reactions with chlorine atoms, hydroxyl radicals, and nitrate radicals
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The rate constants for the gas-phase reactions of di-ferl-butyl ether (DTBE) with chlorine atoms, hydroxyl radicals, and nitrate radicals have been determined in relative rate experiments using FTIR spectroscopy Values of (DTBE→C1) = (1.4 ±0.2) × 10-10, K(DTBE+OH) = (3.7 ±0.7) × 10-12. and K(DTBE+NO3) = (2.8 ±0.9) × 10-16 cm3 molecule-11 s-1 were obtained. Tert-butyl acetate was identified as the major product of both Cl atom and OH radical initiated oxidation of DTBE in air in the presence of NO3 The molar tert-butyl acetate yield was 0.85 ±.0.11 in the Cl atom experiments and 0.84 ±0.11 in OH radical experiments As part of this work the rate constant for reaction of Cl atoms with terl-butyl acetate at 295 K was determined to be (1.6 ±0.3) × 10-11 cm3 molecule 1s-1. The stated errors are two standard deviations (2σ)
- Langer, Sarka,Ljungstroem, Evert,Waengberg, Ingvar,Wallington, Timothy J.,Hurley, Michael D.,Nielsen, Ole John
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p. 299 - 306
(2007/10/03)
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- Reaction of the Nitrate Radical with Some Potential Automotive Fuel Additives. A Kinetic and Mechanistic Study
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Rate coefficients for the reaction of NO3 with ethyl tert-butyl ether (ETBE), diisopropyl ether (DIPE), and tert-amyl methyl ether (TAME) have been determined.Absolute rates were measured at temperatures between 257 and 367 K using the fast flow-discharge (FFD) technique.Relative rate experiments were also performed at 295 K in a reactor equipped with White optics and using FTIR spectroscopy to follow the reactions.Rate data from FFD experiments can be presented as follows: kETBE=(2.48 +/-0.78)E-12exp, kDIPE=(2.02 +/-0.35)E-12exp, and kTAME=(1.21 +/-0.22)E-12exp (in units of cm3 molecule-1 s-1).The rate coefficients at room temperature from the FFD experiments are in goog agreement with the corresponding rate coefficients from the relative experiments.Products from simulated atmospheric oxidation of the investigated ethers, initiated by the reaction with nitrate radical, were identified using FTIR spectroscopy.The degradation of ETBE results in tert-butyl formate, tert-butyl acetate, formaldehyde, and methyl nitrate, that of DIPE in acetone, isopropyl nitrate, isopropyl acetate, and formaldehyde, and that of TAME in tert-amyl formate, formaldehyde, and tert-amyl nitrate.
- Langer, Sarka,Ljundstroem, Evert
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p. 5906 - 5912
(2007/10/02)
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- Formation and Thermal Decomposition of Butyl-Substituted Peroxyacyl Nitrates: n-C4H9C(O)OONO2 and i-C4H9C(O)OONO2
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The butyl-substituted peroxyacyl nitrates n-C4H9C(O)OONO2 and i-C4H9C(O)OONO2 have been synthesized in the liquid phase, prepared in-situ in the gas phase by sunlight irradiation of aldehyde-NO mixtures, measured by electron capture gas chromatography, and characterized in a number of gas-phase and liquid-phase tests. Gas-phase yields as a fraction of initial NO were 0.39 for the n-butyl isomer and 0.20 for the isobutyl isomer. The corresponding gas-phase aldehyde oxidation mechanisms are outlined. Thermal decomposition in the presence of excess NO yielded n-butanal and isobutanal as the major carbonyl products. Thermal decomposition rates at ambient temperature and atmospheric pressure are comparable to that of PAN , with k298 = 1.8E-4 s-1 for n-C4H9C(O)OONO2 and 2.4E-4 s-1 for i-C4H9C(O)OONO2. Emission data for precursor hydrocarbons indicate C4H9C(O)OONO2/PAN ambient concentration ratios of 0.19 in urban air. Atmospheric implications for the formation and removal of C4H9C(O)OONO2 are briefly discussed.
- Grosjean, Daniel,Grosjean, Eric,Williams, Edwin L.
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p. 1099 - 1105
(2007/10/03)
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- FTIR Product Study of the Cl-Initiated Oxidation of C2H5Cl: Reactions of the Alkoxy Radical CH3CHClO
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The Cl-atom-initiated oxidation of C2H5Cl has been investigated at 295 K using Fourier transform infrared (FTIR) spectroscopy.The observed products are HCl, CO2, CH3COCl, HCHO, CO, CH3OH, HCOOH, CH3OOH, CH3C(O)OOH, and CH2ClCHO.The yields of HCl and CO2 per C2H5Cl consumed are surprisingly high, (157 +/- 6) percent and (53 +/- 5) percent, and are constant over the C2H5Cl consumption range of 3 - 15 percent.To rationalize these results, we propose a new alkoxy radical decomposition pathway: the CH3CHClO radical intramolecularly eliminates HCl to produce the acetyl radical, CH3CO, which subsequently reacts to form CO2 and methyl radical oxidation products.As part of this work, a relative rate technique was used to measure the reactivity of Cl atoms toward C2H5Cl, CD3CH2Cl, and CH3COCl.We report k(Cl+C2H5Cl) = (8.7 +/- 1.0) x 10-12, k(Cl+CD3CH2Cl) = (7.3 +/- 1.0) x 10-12 and k(Cl+CH3COCl) -14 (units of cm3 molecule-1 s-1).The implications of our results are discussed in terms of understanding the atmospheric chemistry of halogenated organic compounds.
- Shi, Jichun,Wallington, Timothy J.,Kaiser, E. W.
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p. 6184 - 6192
(2007/10/02)
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- Novel Method for the Measurements of Gas-Phase Peroxy Radical Absorption Spectra
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The pulse radiolysis method has been used to generate methyl peroxy radicals in the presence of high concentrations of NO.The CH3O2 radicals are then rapidly converted to CH3ONO by reaction with NO.Methyl nitrite absorbs strongly in the UV.Hence the initial absorption attributable to CH3O2 is rapidly replaced by absorption by CH3ONO.By varying the monitoring wavelength one can readily determine the isobestic point, where ?(CH3O2) = ?(CH3ONO) + ?(NO2).For methyl peroxy radicals the isobestic point was determined to lie in the wavelength range 228-230 nm, and hence ?(CH3O2) = (3.9 +/- 0.4) x 10-18 cm2 molecule-1.Quoted errors are the sum of statistical (2?) and our estimate of potential systematic errorrs (5percent).As part of the present work rate constants for reactions 11 and 14 at 298 K and 600 mbar total pressure of SF6 were determined to be CH3 + NO + M --> CH3NO + M (11) F + O2 + M --> FO2 + M (14) k11 = (1.07 +/- 0.03) x 10-11 cm3 molecule-1 s-1 and k14 = (2.35 +/- 0.20) x 10-13 cm3 molecule-1 s-1 at 298 K.Results are discussed with respect to previous literature data.
- Wallington, Timothy J.,Maricq, M. Matti,Ellermann, Thomas,Nielsen, Ole J.
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p. 982 - 986
(2007/10/02)
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- Thermal Decomposition of Peroxyacetyl Nitrate in the Presence of O2, NO2 and NO
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The thermal decomposition of pure PAN in N2 as well as in the presence of added O2, NO2 and NO was studied at 1 atm pressure.In addition to methyl nitrate, NO2 was a significant N-product of pure PAN in N2 thermal decomposition.In the presence of sufficiently large amounts of O2, no methyl nitrate was formed at 333 K, indicating that the homolytic PAN decay to methyl nitrate and carbon dioxide is not occurring.In the presence of NO (in contrast to former studies) methyl nitrite was found to be the major organo-nitrogen compound instead of methyl nitrate.The systemPAN-NO-N2 allowed the determination of the rate constant 3.1*10-4 s-1 at 298 K for reaction (1): PAN --> CH3COO2 + NO2, in agreement with prior studies.Computer simulations based on the free radical mechanism starting with reaction (1) fitted very well the experimental results.Keywords: PAN; Thermal decomposition; O2; NO2; NO.
- Roumelis, Nikolaos,Glavas, Sotirios
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- N-NITROHYDRAZINES AND THEIR SALTS
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A method was developed for the synthesis of functionally substituted N-nitrohydrazines by nonacid nitration of the respective silylhydrazines.It was shown that the stability of these compounds increases with increase in the number of electronegative substituents.The first representative of N,N'-dinitrohydrazines, i.e., N,N'-dinitro-N,N'-diacetylhydrazine, was synthesized.Some of the obtained N-nitrohydrazines are characterized by dissociation with the formation of diazenes.The action of nucleophilic reagents on functionally N,N'-disubstituted N-methyl-N'-nitrohydrazines gave the salts of N-nitrohydrazines.
- Kalinin, A. V.,Apasov, E. T.,Ioffe, S. L.,Tartakovskii, V. A.
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p. 988 - 995
(2007/10/02)
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- Rate Constants for the Reactions of CH3O and C2H5O with NO2 over a Range of Temperature and Total Pressure
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The kinetics of the reactions of CH3O and C2H5O radicals with NO2 have been studied using pulsed laser photolysis to create the radicals from the corresponding alkyl nitrite and by time-resolved, laser-induced fluorescence to observe the decay of the radical concentration.At 295 K, rate constants for CH3O+NO2 have been measured in the presence of Ar (6-100Torr), He(30-100 Torr) and CF4 (30-125 Torr).The association reaction to CH3ONO2 appears to predominate, and rate constants in the limit of low and high pressure are deduced: (k0/10E-29 cm6 molecule-2 s-1) =2.8+/-0.6(M=Ar); 1.6 +/- (M=He); 3.4+/-1.0(M=CF4), and (kinfinite/10E-11 cm3 molecule-1 s-1)=2.0+/-0.4, where the quoted errors correspond to two standard deviations.A limited number of measurements is also reported for this reaction at 390K.The rate of the reaction of C2H5O with NO2 at 295 K is found to be same in the presence of 15 and 100 Torr of Ar, and the measurements yield a rate constant: (kinfinite/10E-11 cm3 molecule-1 s-1) =2.8+/-0.3.
- Frost, Michael J.,Smith, Ian W. M.
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p. 1751 - 1756
(2007/10/02)
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- Synthesis and Decomposition of the N-Alkyl-N-nitro-O-benzoylhydroxylamines
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Nitration of N-alkyl-O-benzoylhydroxylamines yields the correspondng N-nitro derivatives.At modest temperatures these compounds decompose to yield alkyl benzoates, alkenes, benzoic acid, and nitrous oxide.In the case of primary alkylnitrohydroxylamines, nitroalkanes and alkyl nitrates are also formed.The alkyl benzoates are products of ionic reactions since skeletal rearrangements characteristics of carbonium ions occur.The insensivity of the rates of decomposition to solvent polarity suggests that the rate-determining step is a rearrangement rather than direct ionization.
- White, Emil H.,Reefer, John,Erickson, Ronald H.,Dzadzic, Petar M.
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p. 4872 - 4876
(2007/10/02)
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- Linear-Reactor-IR.-Matrix and Microwave Spectroscopy of the System O3/NO2/(Z)-2-Butene
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Investigation of the formation of complex reaction products in the gas-phase system O3/NO2/(Z)-2-butene by combination of linear reactors with IR. matrix and microwave Stark spectroscopy is reported.Besides the polyatomic products observed earlier in the gas-phase ozonolysis of (Z)-2-butene, the following products were identified: N2O5, HNO3, HNO4, CH3NO2, CH3ONO, CH3COONO2 and CH3COO2NO2 (peroxyacetyl nitrate PAN).Matrix IR spectra of N2O5, HNO3, CH3COONO, CH3COONO2 required for reference purposes are presented.It is shown that PAN-formation occurs already in the absence of light.A reaction scheme is proposed for explanation of the observed complex NOx-containing products, which assumes methyldioxirane as a central intermediate.Particular reaction steps of the scheme will be discussed, including thermochemical estimates of reaction enthalpies.
- Dommen, Joseph,Forster, Martin,Rupreccht, Heidi,Bauder, Alfred,Guenthard, Hans-Heinrich
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p. 504 - 520
(2007/10/02)
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- Oxidation of Sulfur Dioxide by Methylperoxy Radicals
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This study was made to resolve the apparent discrepancy between the finite rate constants observed for the CH3O2 reaction with SO2 in high-intensity flash photolysis and near zero values observed recently by us and others for this reaction in NO-free, CH3O2-SO2 experiments at low intensity.
- Kan, Charles S.,Calvert, Jack G.,Shaw, John H.
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p. 1126 - 1132
(2007/10/02)
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- Direct vs. Indirect Mechanisms in Organic Electrochemistry. Estimates of Activation Energies for Hydrogen Atom Transfer Processes of Relevance in Indirect Mechanisms Using the Bond Energy-Bond Order (BEBO) and Equibonding Methods
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Activation energies for a number of hydrogen abstraction reactions of interest in mechanistic organic electrochemistry have been calculated using the bond energy-bond-order (BEBO) and equibonding method.The main emphasis has been put on processes with bearing on the problem of deciding between direct and indirect mechanisms in anodic oxidation, viz. acyloxylation, hydroxylation, methoxylation, nitrooxylation, cyanation, carbomethoxylation and azidation.The results indicate that indirect mechanisms might play a more important role than presently assumed.
- Eberson, Lennart
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p. 481 - 492
(2007/10/02)
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