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1.
The rate parameters for the reaction of the OH radical with CH3Br have been measured using the discharge flow-electron paramagnetic resonance method. The result isk 1=(1.86±0.48)×10–12 exp[–(1230±150)/T] cm3 molecule–1 s–1. This value is compared to earlier data and is found to be in excellent agreement with the most recent results, which greatly increases the accuracy of the ozone depletion potential of CH3Br which can be derived from these kinetic data.  相似文献   

2.
The kinetics of the aqueous phase reactions of NO3 radicals with HCOOH/HCOO– and CH3COOH/CH3COO– have been investigated using a laser photolysis/long-path laser absorption technique. NO3 was produced via excimer laser photolysis of peroxodisulfate anions (S2O 8 2– ) at 351 nm followed by the reactions of sulfate radicals (SO 4 – ) with excess nitrate. The time-resolved detection of NO3 was achieved by long-path laser absorption at 632.8 nm. For the reactions of NO3 with formic acid (1) and formate (2) rate coefficients ofk 1=(3.3±1.0)×105 l mol–1 s–1 andk 2=(5.0±0.4)×107 l mol–1 s–1 were found atT=298 K andI=0.19 mol/l. The following Arrhenius expressions were derived:k 1(T)=(3.4±0.3)×1010 exp[–(3400±600)/T] l mol–1 s–1 andk 2(T)=(8.2±0.8)×1010 exp[–(2200±700)/T] l mol–1 s–1. The rate coefficients for the reactions of NO3 with acetic acid (3) and acetate (4) atT=298 K andI=0.19 mol/l were determined as:k 3=(1.3±0.3)×104 l mol–1 s–1 andk 4=(2.3±0.4)×106 l mol–1 s–1. The temperature dependences for these reactions are described by:k 3(T)=(4.9±0.5)×109 exp[–(3800±700)/T] l mol–1 s–1 andk 4(T)=(1.0±0.2)×1012 exp[–(3800±1200)/T] l mol–1 s–1. The differences in reactivity of the anions HCOO– and CH3COO– compared to their corresponding acids HCOOH and CH3COOH are explained by the higher reactivity of NO3 in charge transfer processes compared to H atom abstraction. From a comparison of NO3 reactions with various droplets constituents it is concluded that the reaction of NO3 with HCOO– may present a dominant loss reaction of NO3 in atmospheric droplets.  相似文献   

3.
Rate coefficients have been measured for the gas phasereactions of hydroxyl (OH) radicals and ozone with twounsaturated esters, allyl acetate(CH3C(O)OCH2CH=CH2) and isopropenylacetate (CH3C(O)OC(CH3)=CH2). The OHexperiments were carried out using the pulsed laserphotolysis – laser induced fluorescence technique overthe temperature range 243–372 K and the kinetic dataused to derive the following Arrhenius expressions (inunits of cm3 molecule-1 s-1): allylacetate, k 1 = (2.33 ± 0.27) ×10-12 exp[(732 ± 34)/T]; and isopropenyl acetate,k 2 = (4.52 ± 0.62) × 10-12exp[(809 ± 39)/T]. At 298 K, the rate coefficients obtained (inunits of 10-12 cm3 molecule-1 s-1)are: k 1 = (27.1 ± 3.0) and k 2= (69.6± 9.4). The relative rate technique has been usedto determine rate coefficients for the reaction ofozone with the acetates. Using methyl vinyl ketone asthe reference compound and a value of4.8 × 10-18 cm3 molecule-1s-1 asthe rate coefficient for its reaction with O3,the following rate coefficients were derived at 298 ± 4 K (in units of10-18 cm3molecule-1 s-1): allyl acetate, (2.4 ± 0.7) andisopropenyl acetate (0.7 ± 0.2). Theresults are discussed in terms of structure-activityrelationships and used to derive atmospheric lifetimesfor the acetates.  相似文献   

4.
Rate constants for the reaction of hydroxyl radicals with dibromomethanehave been measured by discharge flow-resonance fluorescence technique(DF-RF) over the temperature range 288–368 K. The derived Arrheniusequation is k1=(1.51 ± 0.37)× 10-12 exp(-(720 ±60)/T) cm3 molec.-1 s-1.The tropospheric lifetime of dibromomethane has been estimated to be 0.29years. An ozone depletion potential (ODP) value of 0.10 for dibromomethanehas been obtained.  相似文献   

5.
Rate coefficients have been measured for the reactions of hydroxyl radicals with a range of aliphatic ethers by a competitive technique. Mixtures of synthetic air containing a few ppm of nitrous acid, isobutene and an ether were photolyzed in a Teflon-bag smog chamber. From the rates of depletion of the ether and of the isobutene, and based on the value of the rate coefficient k(OH+i-C4H8)=5.26×10-11 cm3 molecule-1 s-1, the following rate coefficients were obtained for the hydroxyl radical reactions at 750 Torr and at 294±2K in units of 10-12 cm3 molecule-1 s-1: diethylether = 12.0±1.1, di-n-propylether = 15.3±1.6, di-n-butylether=17.1±0.9, ethyl n-butylether = 13.5±0.4, ethyl t-butyl-ether = 5.6±0.5, and di-isobutylether = 26.1±1.6. The quoted error limits correspond to 2 standard deviations but do not include any contribution from k(OH+i-C4H8) for which the error limits are estimated to be about ±10%. The results are discussed in relation to the available literature data and considered in terms of the structure-activity relation for hydroxyl radical reactions with organic molecules.  相似文献   

6.
Rate constants for the gas-phase reactions of OH radicals, NO3 radicals and O3 with the C7-carbonyl compounds 4-methylenehex-5-enal [CH2=CHC(=CH2)CH2CH2CHO], (3Z)- and (3E)-4-methylhexa-3,5-dienal [CH2=CHC(CH3)=CHCH2CHO] and 4-methylcyclohex-3-en-1-one, which are products of the atmospheric degradations of myrcene, Z- and E-ocimene and terpinolene, respectively, have been measured at 296 ± 2 K and atmospheric pressure of air using relative rate methods. The rate constants obtained (in cm3 molecule–1 s–1 units) were: for 4-methylenehex-5-enal, (1.55 ± 0.15) × 10–10, (4.75 ± 0.35) × 10–13 and (1.46 ± 0.12) × 10–17 for the OH radical, NO3 radical and O3 reactions, respectively; for (3Z)-4-methylhexa-3,5-dienal: (1.61 ± 0.35) × 10–10, (2.17 ± 0.30) × 10–12, and (4.13 ± 0.81) × 10–17 for the OH radical, NO3 radical and O3 reactions, respectively; for (3E)-4-methylhexa-3,5-dienal: (2.52 ± 0.65) × 10–10, (1.75 ± 0.27) × 10–12, and (5.36 ± 0.28) × 10–17 for the OH radical, NO3 radical and O3 reactions, respectively; and for 4-methylcyclohex-3-en-1-one: (1.10 ± 0.19) × 10–10, (1.81 ± 0.35) × 10–12, and (6.98 ± 0.40) × 10–17 for the OH radical, NO3 radical and O3 reactions, respectively. These carbonyl compounds are all reactive in the troposphere, with daytime reaction with the OH radical and nighttime reaction with the NO3 radical being predicted to dominate as loss processes and with estimated lifetimes of about an hour or less.  相似文献   

7.
The reaction of Cl with cyclohexanone (1) was investigated, for the first time, as a function of temperature (273–333 K) and at a low total pressure (1 Torr) with helium as a carrier gas using a discharge flow-mass spectrometry technique (DF-MS). The resulting Arrhenius expression is proposed, k 1= (7.7 ± 4.1) × 10–10 exp[–(540 ± 169)/T]. We also report a mechanistic study with the quantitative determination of the products of the reaction of Cl with cyclohexanone. The absolute rate constant derived from this study at 1 Torr of total pressure and room temperature is (1.3 ± 0.2) × 10–10 cm3 molecule–1 s–1. A yield of 0.94 ± 0.10 was found for the H-abstraction channel giving HCl. In relative studies, using a newly constructed relative rate system, the decay of cyclohexanone was followed by gas chromatography coupled with flame-ionisation detection. These relative measurements were performed at atmospheric pressure with synthetic air and room temperature. Rate constant measured using the relative method for reaction (1) is: (1.7 ± 0.3) × 10–10 cm3 molecule–1 s–1. Finally, results and atmospheric implications are discussed and compared with the reactivity with OH radicals.  相似文献   

8.
Accurate values for the rate and temperature dependence of the reaction NO + O3 NO2 + O2 are important in the chemical modelling of photochemical processes in the atmosphere. Previous measurements have been made at low total pressures and/or with very large mixing ratios relative to those observed in the atmosphere. In this study the reaction rate has been measured using a novel approach under tropospheric conditions of temperature and pressure, and at tens of ppb (mixing ratios of 1 in 108) between 263 and 328 K. The resultant Arrhenius expression (k=Ae-Ea/RT) gives a larger activation energy (Ea/R=1670 ± 100) than the recommended literature value (Ea/R=1400 ± 200), and a larger pre-exponential factor (A=5.1 ± 1.6 × 10-12 cf. recommended A=2.0 × 10-12), but the second-order rate constant at 298 K (1.90 × 10-14 molecules cm-3 s-1 ± 10%) is similar to the recommended value. The results confirm a lack of pressure dependence of the reaction, but were made over too small a range in temperature to address the issue of curvature of the simple Arrhenius expression.  相似文献   

9.
The following temperature-dependent rate coefficients (k/cm3 molecule–1 s–1) of the reactions of hydroxyl radicals with aliphatic ethers have been determined over the temperature range 247–373 K by a competitive flow technique: diethyl ether,k OH=5.2×10–12 exp[(262±150)/T]; methyln-butyl ether,k OH=5.4×10–12 exp[(309±150)/T]; ethyln-butyl ether,k OH=7.3×10–12 exp[(335±150)/T]; di-n-butyl ether,k OH=5.5×10–12 exp[(502±150)/T] and di-n-pentyl ether,k OH=8.5×10–12 exp[(417±150)/T]. The data have been measured relative to the rate coefficientk(OH + 2,3-dimethylbutane)=6.2×10–12 cm3 molecule–1 s–1 independent of temperature.Previous discrepancies in the room-temperature rate coefficients for the OH reactions with ethyln-butyl ether and di-n-butyl ether, obtained in the flow and static experiments of Bennett and Kerr (J. Atmos. Chem. 8, 87–94, 1989;10, 29–38, 1990) compared with those of Wallingtonet al. (Int. J. Chem. Kinet. 20, 541–547, 1988;21, 993–1001, 1989) and of Nelsonet al. (Int. J. Chem. Kinet. 22, 1111–1126, 1990) have been resolved. The results are considered in relation to the available literature data and evaluated rate expressions are deduced where possible. The data are also discussed in terms of structure-activity relationships.  相似文献   

10.
The reactivity of some selected biogenic monoterpenecompounds towards important aqueous phase free-radicaloxidants, namely OH· and SO4 -·, have beeninvestigated using the complementary experimentaltechniques of pulse radiolysis and laser flashphotolysis ( = 248 nm). Rate constants forthe reactions of the OH· radical with cis-verbenol andmethacrolein have been determined to be (6.8 ± 0.5) ×109 dm3 mol-1 s-1 and (8.0± 0.7) × 109 dm3 mol-1s-1,respectively (T = 20 °C, pH 4.0, Ionic strength 0 mol dm-3). Rate constants and activationenergies for the reactions of the SO4 -·radical have been measured for the following compounds(T = 20 °C, pH 4.0, Ionic strength = 0.03 moldm-3): -pinene (k = (3.1 ± 0.1) ×109 dm3 mol-1 s-1;E act. =(8.9 ± 1.3) kJ mol-1), -terpineol(k = (4.1 ± 0.1) × 109 dm3mol-1s-1; E act. = (13.4 ± 0.6) kJmol-1), cis-verbenol (k = (3.2 ± 0.2) ×109 dm3 mol-1 s-1;E act. =(10.0 ± 0.7) kJ mol-1), verbenone (k = (1.6± 0.1) × 109 dm3 mol-1s-1;E act. = (6.1 ± 0.7) kJ mol-1), myrtenal(k = (1.85 ± 0.1) × 109 dm3mol-1s-1; E act. = (7.5 ± 0.7) kJmol-1)and methacrolein (k = (1.18 ± 0.1) × 109dm3 mol-1 s-1). In most instances theabsorption spectra of the intermediate products formedby these reactions have been measured which, inconjunction with strategic conductiometric studies,have been used to suggest plausible mechanisms for theoxidation in acidic de-oxygenated solution.  相似文献   

11.
The relative rate technique has been used to measure rate constants for the reaction of chlorine atoms with peroxyacetylnitrate (PAN), peroxypropionylnitrate (PPN), methylhydroperoxide, formic acid, acetone and butanone. Decay rates of these organic species were measured relative to one or more of the following reference compounds; ethene, ethane, chloroethane, chloromethane, and methane. Using rate constants of 9.29×10–11, 5.7×10–11, 8.04×10–12, 4.9×10–13, and 1.0×10–13 cm3 molecule–1 sec–1 for the reaction of Cl atoms with ethene, ethane, chloroethane, chloromethane, and methane respectively, the following rate constants were derived, in units of cm3 molecule–1 s–1: PAN, <7×10–15; PPN, (1.14±0.12)×10–12; HCOOH, (2.00±0.25)×10–13; CH3OOH, (5.70±0.23)×10–11; CH3COCH3, (2.37±0.12)×10–12; and CH3COC2H5, (4.13±0.57)×10–11. Quoted errors represent 2 and do not include possible systematic errors due to errors in the reference rate constants. Experiments were performed at 295±2 K and 700 torr total pressure of nitrogen or synthetic air. The results are discussed with respect to the previous literature data and to the modelling of nonmethane hydrocarbon oxidation in the atmosphere.In recent discussions with Dr. R. A. Cox of Harwell Laboratory, UKAEA, we learnt of a preliminary value for the rate constant of the reaction of Cl with acetone of (2.5±1.0)×10–12 cm3 molecule–1 sec–1 measured by R. A. Cox, M. E. Jenkin, and G. D. Hayman using molecular modulation techniques. This value is in good agreement with our results.  相似文献   

12.
Rate constants for the gas-phase reactions of OH radicals with nopinone (6,6-dimethylbicyclo[3.1.1]heptan-2-one) and camphenilone (3,3-dimethylbicyclo[2.2.1]heptan-2-one) and for the reactions of 4-acetyl-1-methylcyclohexene with OH and NO3 radicals and O3 have been measured at 296±2 K. The rate constants (cm3 molecule–1 s–1 units) obtained were, for reaction with the OH radical: nopinone, (1.43±0.37)×10–11; camphenilone, (5.15±1.44)×10–12; and 4-acetyl-1-methylcyclohexene, (1.29±0.33)×10–10; for reaction with the NO3 radical: 4-acetyl-1-methylcyclohexene, (1.05±0.38)×10–11; and for reaction with O3: 4-acetyl-1-methylcyclohexene, (1.50±0.53)×10–16. These data are used to calculate the tropospheric lifetimes of these monoterpene atmospheric reaction products.  相似文献   

13.
A discharge-flow tube coupled with resonance fluorescence and chemiluminescence detection has been used to investigate the reactions IO + HO2 products (1) and IO + O(3P) I + O2(2), at T = 296 ± 1 K and P = 1.7 - 2 Torr. The rate constants k-1 and k2 have been found to be (7.1 ± 1.6) × 10-11 cm3 molecule-1 s-1 and (1.35 ± 0.15) × 10-10 cm3 molecule-1 s-1, respectively.  相似文献   

14.
Barnes  I.  Bastian  V.  Becker  K. H.  Fink  E. H.  Nelsen  W. 《Journal of Atmospheric Chemistry》1986,4(4):445-466
The reactions of OH radicals with SO2, H2S, thiophenol, and a series of aliphatic thiols (1–5 C-atoms) have been investigated in 201 and 381 reaction chambers at 1 atm total pressure and 300 K using a competitive kinetic technique. Initially, OH radicals were produced by photolysis of CH3ONO/NO mixtures in air. Applying this OH source rate constants for OH with SO2, H2S, and thiophenol in synthetic air were determined to be (1.1±0.2)×10-12, (5.5±0.8)×10-12 and (1.1±0.2)×10-11 cm3 s-1, respectively. However, when this method was applied to the aliphatic thiols the rate constants obtained were found to be dependent on the partial pressures of O2 and NO. These effects have been attributed to the built-up of a radical species, not yet identified, which leads to uncontrolled chain reactions in the system. Using the photolysis of H2O2 at wavelengths greater than 260 nm as the OH source in 1 atm N2, rate constants for the 1–5 aliphatic thiols in the range 2.9 to 5.6×10-11 cm3 s-1 were obtained. The rate constants obtained in the present study are compared with recent literature values.  相似文献   

15.
Rate constants for the reaction of OH radicals with some branched alkyl nitrates have been measured applying a competitive technique. Methyl nitrite photolysis in synthetic air was used as OH radical source at 295±2 K and 1000 mbar total pressure. Using a rate constant of 2.53×10-12 cm3 s-1 for the reaction of OH radicals with n-butane as reference, the following rate constants were obtained (units: 10-12 cm3 s-1): isopropyl nitrate, 0.59±0.22; isobutyl nitrate, 1.63±0.20; 3-methyl-2-butyl nitrate, 1.95±0.15; 2-methyl-1-butyl nitrate, 2.50±0.15; 3-methyl-1-butyl nitrate, 2.55±0.35. These values have been combined with the literature data to recalculate the substituent factors F(X) for the different nitrate groups which can be used to predict OH rate constants for organic nitrates for which experimental data are not available.Preliminary measurements of the photolysis frequency of isopropyl nitrate have shown that for this nitrate as a model substance, OH reactions and direct photolysis are of equal importance under tropospheric conditions.  相似文献   

16.
A combined study of the OH gas phase reaction and uptake on aqueous surfacesof two carbonates, dimethyl and diethyl carbonate has been carried out todetermine the atmospheric lifetimes of these compounds. Rate coefficients havebeen measured for gas phase reactions of OH radicals with dimethyl and diethylcarbonate. The experiments were carried out using pulsed laser photolysis– laser induced fluorescence over the temperature range 263–372K and the kinetic data were used to derive the following Arrhenius expressions(in units of cm3 molecule–1 s–1):for dimethyl carbonate, k1 = (0.83±0.27)×10–12 exp [–(247± 98)/T] and fordiethyl carbonate, k2 = (0.46±0.15)×10–12 exp [(503± 203)/T]. At 298 K, therate coefficients obtained (in units of 10–12 cm3molecule–1 s–1) are: k1 =(0.35± 0.04) and k2 = (2.31± 0.29). The results arediscussed in terms of structure-activity relationships.The uptake coefficients of both carbonates on aqueous surfaces were measuredas a function of temperature and composition of the liquid phase, using thedroplet train technique coupled to a mass spectrometric detection. Dimethyland diethyl carbonate show very similar results. For both carbonates, themeasured uptake kinetics were found to be independent of the aqueous phasecomposition (pure water, NaOH solutions) but dependent on gas-liquid contacttime which characterises a surface saturation effect. The uptake coefficientvalues show a slight negative temperature dependence for both carbonates.These values vary from 1.4×10–2 to0.6×10–2 in the temperature range of 265–279 Kfor dimethyl carbonate, from 2.4×10–2 to0.9×10–2 in the temperature range of 270–279 Kfor diethyl carbonate. From the kinetic data, the following Henry's lawconstants were derived between 279 and 265 K: dimethyl carbonate,H1 = 20–106 M atm–1; and diethyl carbonate,H2 = 30–98 M atm–1. The reported data showthat the OH reaction is the major atmospheric loss process of these twocarbonates with lifetimes of 33 and 5 days, respectively, while the wetdeposition is a negligible process.  相似文献   

17.
Kinetics and products of the gas-phase reactions of dimethylsulphide (DMS), dimethylsulphoxide (DMSO) and dimethylsulphone (DMSO2) with Br atoms and BrO radicals in air have beeninvestigated using on-line Fourier Transform Infrared Spectroscopy (FT-IR) as analytical technique at 740 ± 5 Torr total pressure and at 296 ± 3 K in a480 L reaction chamber. Using a relative rate method for determining the rate constants; the following values (expressed in cm3molecule–1 s–1) were found: kDMS+Br = (4.9 ±1.0) ×10–14, kDMSO + Br < 6 × 10–14,kDMSO 2 + Br 1 × 10–15,kDMSO + BrO = (1.0 ± 0.3) × 10–14 andkDMSO 2 + BrO 3 × 10–15 (allvalues are given with one on the experimental data). DMSO, SO2, COS, CH3SBr andCH3SO2Br were identified as the main sulphur containing products of the oxidation of DMS by Br atoms. From the reaction between DMSO and Br atoms, DMSO2and CH3SO2Br were the only sulphur containing products thatwere identified. DMSO, DMSO2 and SO2 were identified as themain sulphur containing products of the reaction between DMS and BrO.DMSO2 was found to be the only product of the reaction between DMSO and BrO. For the reactions of DMSO2 with Br and BrO no products were identified because the reactions were too slow.The implications of these results for atmospheric chemistry are discussed.  相似文献   

18.
A statistically relevant correlation between the reaction rate coefficient, k OH, for the OH radical reaction with 161 organic compounds in the gas phase at 300 K, and the corresponding vertical ionisation energies E i,v, reveals two classes of compounds: aromatics where –log(k OH/cm3s-1)3/2E i,v(eV)–2 and aliphatics where –log(k OH/cm3s-1)4/5E i,v(eV)+3. The prediction of the rate coefficient, k OH, for the reaction of OH with organic molecules from the above equations has a probability of about 90%. Assuming a global diurnal mean of the OH radical concentration of 5×105 cm3, the upper limit of the tropospheric half-life of organic compounds and their persistence can be estimated.  相似文献   

19.
The absolute rate constants for the gas-phasereactions of the NO3 radical with a series ofaldehydes such as acetaldehyde, propanal, butanal,pentanal, hexanal and, heptanal were measured overthe temperature range 298–433 K, using a dischargeflow system and monitoring the NO3 radical byLaser Induced Fluorescence (LIF).The measured rate constants at 298 K for thereaction of NO3, in units of 10–14 cm3molecule–1 s–1, were as follows:acetaldehyde 0.32 ± 0.04, propanal 0.60 ± 0.06, butanal 1.46± 0.16, pentanal 1.75 ±0.06, hexanal 1.83 ± 0.36, and heptanal 2.37 ±0.42. The proposed Arrhenius expressions arek1 = (6.2 ± 7.5) × 10–11 exp[–(2826 ± 866)/T] (cm3 molecule–1s–1),k2 = (1.7 ± 1.0) × 10–11 exp[–(2250 ± 192)/T] (cm3 molecule–1s1), k3 =(7.6 ± 9.8) × 1011 exp[–(2466 ± 505)/T] (cm3 molecule–1s–1),k4 = (2.8 ± 1.4) × 10–11 exp[–(2189 ± 156)/T] (cm3 molecule–1s–1), k5 = (7.0 ± 1.8) ×10–11 exp [–(2382 ± 998)/T](cm3 molecule–1 s–1), andk6 = (7.8 ± 1.0) × 10–11 exp[–(2406 ± 481)/T](cm3 molecule–1 s–1).Tropospheric lifetimes for these aldehydes werecalculated at night and during the day for typicalNO3 and OH average concentrations and showed thatboth radicals provide an effective tropospheric sinkfor these compounds and that the night-time reactionwith the NO3 radical can be an important, if notdominant, loss process for these emitted organics andfor NO3 radicals.  相似文献   

20.
The activation of Br- and Cl- to atomic Br and Cl in sea-spray aerosol was investigated in smog-chamber experiments. In the presence of O3, hydrocarbons and NaCl aerosol alone no activation was observed. By adding Br- to the aerosol, the chain reaction: Br + O3 BrO, BrO + HO2 HOBr, HOBr HOBr(aq), HOBr(aq) + H+ + Br- Br2 (6), HOBr(aq) + H+ + Cl- BrCl (7) was verified. The step from reaction (6) to (7) is accompanied by a decrease of the Br-/Cl- ratio from 1/600 to less than 1/2000. In the absence of sulphate, the chain is initiated by the reaction of OH(aq) with Br-. The pH value decreases to less than 2 during the first minutes of the experiment and later on to almost 1 (in the absence of NOx or SO2). This is caused by the formation of oxalic acid from alkanes and toluene. In stopped flow experiments, the reduction of Br2 by oxalic acid was observed to occur through a two-step mechanism: HC2O4 - + Br2 Br- + BrC2O4H (k22, k-22), BrC2O4H Br- + H+ + 2 CO2 (23) with the following rate constants and ratios of rate constants, k ± 2: k22k-23 / k-22 = (2.9 ± 0.3) · 10-4 s-1, k-22 / k-23 = 7000 ± 3000 13000 M-1, k22 = 2 ±-1 4 M-1 s-1, and k-23 > 0.1 s-1, k-22 > 600 M-1 s-1. Oxalic acid may be responsible for the inhibition of the chain reaction observed at the end of the experiments.  相似文献   

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