Reaction Of Cl Atoms Research Articles

Kinetic studies of Cl reactions with 3-buten-1-ol and 2-buten-1-ol over the temperature range 298–363 K

Using the relative rate method, the rate coefficients for gas phase reactions of Cl atoms with two unsaturated alcohols, 3-buten-1-ol ( k 1) and 2-buten-1-ol ( k 2), were determined in 760 Torr of purified air over the temperature range of 298–363 K. At 298 K, the measured rate coefficients (in units of cm 3 molecule −1 s −1) were found to be: k 1 = (2.63 ± 0.25) × 10 −10 and k 2 = (3.90 ± 0.35) × 10 −10. The values obtained are discussed and compared with the previous determinations.

Atmospheric Chemistry of CF3CF═CH2 and (Z)-CF3CF═CHF: Cl and NO3 Rate Coefficients, Cl Reaction Product Yields, and Thermochemical Calculations

Rate coefficients, k, for the gas-phase reactions of Cl atoms and NO(3) radicals with 2,3,3,3-tetrafluoropropene, CF(3)CF═CH(2) (HFO-1234yf), and 1,2,3,3,3-pentafluoropropene, (Z)-CF(3)CF═CHF (HFO-1225ye), are reported. Cl-atom rate coefficients were measured in the fall-off region as a function of temperature (220-380 K) and pressure (50-630 Torr; N(2), O(2), and synthetic air) using a relative rate method. The measured rate coefficients are well represented by the fall-off parameters k(0)(T) = 6.5 × 10(-28) (T/300)(-6.9) cm(6) molecule(-2) s(-1) and k(∞)(T) = 7.7 × 10(-11) (T/300)(-0.65) cm(3) molecule(-1) s(-1) for CF(3)CF═CH(2) and k(0)(T) = 3 × 10(-27) (T/300)(-6.5) cm(6) molecule(-2) s(-1) and k(∞)(T) = 4.15 × 10(-11) (T/300)(-0.5) cm(3) molecule(-1) s(-1) for (Z)-CF(3)C═CHF with F(c) = 0.6. Reaction product yields were measured in the presence of O(2) to be (98 ± 7)% for CF(3)C(O)F and (61 ± 4)% for HC(O)Cl in the CF(3)CF═CH(2) reaction and (108 ± 8)% for CF(3)C(O)F and (112 ± 8)% for HC(O)F in the (Z)-CF(3)CF═CHF reaction, where the quoted uncertainties are 2σ (95% confidence level) and include estimated systematic errors. NO(3) reaction rate coefficients were determined using absolute and relative rate methods. Absolute measurements yielded upper limits for both reactions between 233 and 353 K, while the relative rate measurements yielded k(3)(295 K) = (2.6 ± 0.25) × 10(-17) cm(3) molecule(-1) s(-1) and k(4)(295 K) = (4.2 ± 0.5) × 10(-18) cm(3) molecule(-1) s(-1) for CF(3)CF═CH(2) and (Z)-CF(3)CF═CHF, respectively. The Cl-atom reaction with CF(3)CF═CH(2) and (Z)-CF(3)CF═CHF leads to decreases in their atmospheric lifetimes and global warming potentials and formation of a chlorine-containing product, HC(O)Cl, for CF(3)CF═CH(2). The NO(3) reaction has been shown to have a negligible impact on the atmospheric lifetimes of CF(3)CF═CH(2) and (Z)-CF(3)CF═CHF. The energetics for the reaction of Cl, NO(3), and OH with CF(3)CF═CH(2) and (Z)-CF(3)CF═CHF in the presence of O(2) were investigated using density functional theory (DFT).

Products and mechanism of the Cl-initiated atmospheric oxidation of furan: A theoretical study

The products and mechanism of the reaction of Cl atoms with furan on the ground potential energy surface (PES) have been studied by high level quantum chemical methods. The PESs for the Cl + furan reaction in the presence of O 2/CH 3O 2 have been constructed at the CCSD(T)/6-311+g(d,p) level of theory on the basis of the geometric parameters optimized at the MP2(full)/6-311+g(d,p) level of theory. The calculations indicate that the reaction of Cl atoms with furan proceeds mainly by initial addition of Cl atoms to the unsaturated carbon atoms of the furan ring, followed by the formation of two Cl–furan adducts IM1 and IM2 ( ▪ and ▪). Under atmospheric conditions, the Cl–furan adduct IM1 can react further with O 2/CH 3O 2 to generate the major product P5 (5-chloro-2(5H)-furanone, ▪) and the secondary product P6 (butenedial, C(O)HCH CHC(O)H). The calculated results are consistent with the available experimental observations. Moreover, the additional product P5A (2-chloro-3(2H)-furanone, ▪) is also predicted.

Kinetics of the gas-phase reactions of some unsaturated alcohols with Cl atoms and O3

Abstract Reactions of Cl atoms with 3-buten-1-ol, 3-methyl-3-buten-1-ol, 2-methyl-3-buten-1-ol and 4-penten-2-ol were investigated using relative technique with gas chromatograph coupled with flame ionization detection (GC-FID). At 298 ± 1 K and 1.01 × 10 5 Pa, the rate coefficients measured (in units of 10 −10 cm 3 molecule −1 s −1 ) were 3.63 ± 0.49, 4.13 ± 0.56, 3.51 ± 0.48, and 3.62 ± 0.49, respectively. The quoted errors included 2σ from the least-squares analysis and also 10% errors caused by the uncertainty of the reference rate coefficients. In addition, rate coefficients for reactions of the unsaturated alcohols with O 3 were determined using absolute method. The values obtained have been presented, compared with those of their alkene structural homologues and discussed. Reactivity trends and atmospheric implications have also been discussed.

Imaging the nature of the mode-specific chemistry in the reaction of Cl atom with antisymmetric stretch-excited CH4

Following up our preliminary communication [Kawamata et al., Phys. Chem. Chem. Phys. 10, 4378 (2008)], the effects of the antisymmetric-stretching excitation of methane on the Cl((2)P(3/2))+CH(4) reaction are examined here over a wide range of initial collision energy in a crossed molecular beam imaging experiment. The antisymmetric stretch of CH(4) is prepared in a single rovibrational state of (v(3)=1, j=2) by direct infrared absorption, and the major product states of CH(3)(v=0) are probed by a time-sliced velocity-map imaging method. We find that at fixed collision energies, the stretching excitation promotes reaction rate. Compared to the ground-state reaction, this vibrational enhancement factor is, however, no more effective than the translational enhancement. The correlated HCl(v'=1) vibrational branching fraction shows a striking dependence on collision energies, varying from 0.7 at E(c)=2 kcal mol(-1) to about 0.2 at 13 kcal mol(-1). This behavior resembles the previously studied Cl+CH(2)D(2)(v(6)=1), but is in sharp contrast to the Cl+CHD(3)(v(1)=1) and CH(2)D(2)(v(1)=1) reactions. Dependences of experimental results on the probed rotational states of CH(3)(v=0) are also elucidated. We qualitatively interpret those experimental observations based on a conceptual framework proposed recently.

Erratum: “Kinetics of the gas-phase reactions of Cl atom with selected C2-C5 unsaturated hydrocarbons at 283 < T < 323 K,” Int J Chem Kinet 2000, 32, 478

Erratum: “Kinetics of the gas-phase reactions of Cl atom with selected C2-C5 unsaturated hydrocarbons at 283 < T < 323 K,” Int J Chem Kinet 2000, 32, 478

ChemInform Abstract: Rate Constants for the Gas-Phase Reactions of OH Radicals and Cl Atoms with n-Alkyl Nitrites at Atmospheric Pressure and 298 K.

Rate constants for the reactions of OH radicals and Cl atoms with CH3ONO, C2H5ONO, n-C3H7ONO, n-C4H9ONO, and n-C5H11ONO have been determined at 298 ± 2 K and a total pressure of approximately 1 atm. The OH rate data were obtained using both the absolute rate technique of pulse radiolysis combined with kinetic spectroscopy and a relative rate method involving simultaneous measurement of the loss of the nitrite and the reference compound. The Cl rate constants were measured using the relative rate method. Values of the rate constants in units of 10−13 cm3 molecule−1 s−1 are: Text Table Text. Relative Cl Relative OH Absolute OH CH3ONO 94.4 ± 7.4 3.0 ± 1.0 2.6 ± 0.5 C2H5ONO 295 ± 13 7.0 ± 1.5 7.0 −1.1 n-C3H7ONO 646 ± 58 11.0 ± 1.5 12.0 ± 0.5 n-C4H9ONO 1370 ± 58 22.7 ± 0.8 27.2 ± 6.0 n-C5H11ONO 2464 ± 444 37.4 ± 5.0 42.5 ± 8.0 When compared to rate data for the corresponding alkanes the results show that the -ONO group decreases the rate constant for H atom abstraction by the OH radical from groups bonded to the -ONO group and also decreases that for groups in the β position. Similar results were found for the reaction of Cl atoms with these compounds. The results are discussed in terms of reactivity trends.

ChemInform Abstract: Rate Constants for the Gas-Phase Reactions of Cl Atoms with a Series of Hydrofluorocarbons and Hydrochlorofluorocarbons at 298 .+-.2 K.

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FTIR Product Distribution Study of the Cl and OH Initiated Degradation of Methyl Acrylate at Atmospheric Pressure

A product study is reported on the gas-phase reactions of OH radicals and Cl atoms with methyl acrylate. The experiments were performed in a 1080-L quartz-glass chamber in synthetic air at 298 ± 2 K and 760 ± 10 Torr using long-path in situ FTIR spectroscopy for the analysis of the reactants and products. In the absence of NO(x) the major product observed in the OH reaction is methyl glyoxylate, with formaldehyde as a coproduct. For the reaction with Cl only formyl chloride (HC(O)Cl), CO, and HCl could be positively identified as products, however, the concentration-time behavior of these products show that they are secondary products and originate from the further oxidation of a major primary product. From this behavior and a comparison with simulated spectra unidentified bands in the residual product spectra are tentatively attributed to a compound of structure CH(2)ClC(O)C(O)OCH(3), i.e., formation of methyl 3-chloro-2-oxopropanoate from the reaction of Cl with methyl acrylate. The present results are compared with previous results where available and simple atmospheric degradation mechanisms are postulated to explain the formation of the observed products.

Temperature‐dependent rate coefficients and mechanism for the gas‐phase reaction of chlorine atoms with acetone

AbstractThe rate coefficient for the gas‐phase reaction of chlorine atoms with acetone was determined as a function of temperature (273–363 K) and pressure (0.002–700 Torr) using complementary absolute and relative rate methods. Absolute rate measurements were performed at the low‐pressure regime (∼2 mTorr), employing the very low pressure reactor coupled with quadrupole mass spectrometry (VLPR/QMS) technique. The absolute rate coefficient was given by the Arrhenius expression k(T) = (1.68 ± 0.27) × 10−11 exp[−(608 ± 16)/T] cm3 molecule−1 s−1 and k(298 K) = (2.17 ± 0.19) × 10−12 cm3 molecule−1 s−1. The quoted uncertainties are the 2σ (95% level of confidence), including estimated systematic uncertainties. The hydrogen abstraction pathway leading to HCl was the predominant pathway, whereas the reaction channel of acetyl chloride formation (CH3C(O)Cl) was determined to be less than 0.1%. In addition, relative rate measurements were performed by employing a static thermostated photochemical reactor coupled with FTIR spectroscopy (TPCR/FTIR) technique. The reactions of Cl atoms with CHF2CH2OH (3) and ClCH2CH2Cl (4) were used as reference reactions with k3(T) = (2.61 ± 0.49) × 10−11 exp[−(662 ± 60)/T] and k4(T) = (4.93 ± 0.96) × 10−11 exp[−(1087 ± 68)/T] cm3 molecule−1 s−1, respectively. The relative rate coefficients were independent of pressure over the range 30–700 Torr, and the temperature dependence was given by the expression k(T) = (3.43 ± 0.75) × 10−11 exp[−(830 ± 68)/T] cm3 molecule−1 s−1 and k(298 K) = (2.18 ± 0.03) × 10−12 cm3 molecule−1 s−1. The quoted errors limits (2σ) are at the 95% level of confidence and do not include systematic uncertainties. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 724–734, 2010

Product distribution in the Cl‐initiated photooxidation of CF3C(O)OCH2CF3

AbstractThe product distribution and the mechanism of the reaction of Cl atoms with 2,2,2‐trifluoroethyl 2,2,2‐trifluoroacetate (TFETFA; CF3C(O)OCH2CF3) were investigated using a 1080 L environmental chamber with in situ Fourier transform infrared (FTIR) spectroscopy detection. The experiments were performed at (296 ± 2) K and atmospheric pressure (760 ± 10) Torr of synthetic air free of NOx. A yield of (45 ± 3)% was obtained for the CF3C(O)OC(O)CF3 formation. CF2O and CO were produced with estimated yields of 35 and 28%, respectively. No trifluoroacetic acid (TFA; CF3C(O)OH) was observed. The yields determined are rationalized in terms of the competitive reaction channels for the fluoroalcoxy radicals formed in the H‐abstraction process: (a) reaction with O2, (b) CC, CO, CH decomposition, and (c) a possible α‐ester rearrangement pathway. The negligible importance of the α‐ester channel, to produce TFA, was explained by the reduction of the stability of the five‐membered transition state of the α‐ester rearrangement. Atmospheric implications, particularly regarding the fluorocarboxylic acid formation, are discussed. Copyright © 2010 John Wiley & Sons, Ltd.

Kinetics of the Reactions of Cl Atoms with Several Ethers

The reactions of Cl with tetrahydrofuran, tetrahydropyran, and dimethyl ether have been studied as a function of temperature, pressure, and O(2) concentration. The temperature was varied from approximately 280 to 360 K, the mole fraction of O(2) ranged from zero to approximately 0.6, and the experiments were made in a bath of argon at total pressures ranging from approximately 300 to 760 Torr. The rate coefficients were measured using the relative rate method with gas chromatographic analysis. The reaction of Cl with isobutane was the reference reaction, the rate coefficients for which were calibrated against the reaction of propane with chlorine atoms as a function of temperature. The rate coefficients were unaffected by the concentration of O(2) or by variation in pressure. The rate coefficient for the reaction of Cl with isobutane increased slightly with decreasing temperature. This weak temperature dependence of the rate coefficient was in satisfactory agreement with information in the literature and is represented in Arrhenius form by k(T) = (1.02(-0.25)(+0.32)) x 10(-10) exp(99 +/- 88/T) cm(3) molecule(-1) s(-1), where the uncertainties represent two standard deviations. The rate coefficients for the reactions of Cl with the ethers did not show a statistically significant dependence on temperature. Their average values over our range of temperature are: for Cl + tetrahydrofuran, k = (2.71 +/- 0.34) x 10(-10) cm(3) molecule(-1) s(-1); for Cl + tetrahydropyran, k = (2.03 +/- 0.82) x 10(-10) cm(3) molecule(-1) s(-1); and for Cl + dimethyl ether, k = (1.73 +/- 0.22) x 10(-10) cm(3) molecule(-1) s(-1), in which the uncertainties are again two standard deviations.

Velocity map imaging the dynamics of the reactions of Cl atoms with neopentane and tetramethylsilane

The reactions of ground state Cl((2)P(3/2)) atoms with neopentane and tetramethylsilane have been studied at collision energies of 7.9+/-2.0 and 8.2+/-2.0 kcal mol(-1), respectively. The nascent HCl(v=0,J) products were probed using resonance enhanced multiphoton ionization spectroscopy combined with velocity map imaging (VMI) to determine the rotational level population distributions, differential cross sections (DCSs), and product translational energy distributions. The outcomes from PHOTOLOC and dual beam methods are compared and are discussed in light of previous studies of the reactions of Cl atoms with other saturated hydrocarbons, including a recent crossed molecular beam and VMI investigation of the reaction of Cl atoms with neopentane [Estillore et al., J. Chem. Phys. 132, 164313 (2010)]. Rotational distributions were observed to be cold, consistent with the reactions proceeding via a transition state with a collinear Cl-H-C moiety. The DCSs for both reactions are forward peaked but show scatter across a broad angular range. Interpretation using a model based on linear dependence of scattering angle on impact parameter indicates that the probability of reaction is approximately constant across all allowed impact parameters. Product translational energy distributions from dual beam experiments have mean values, expressed as fractions of the total available energy, of 0.67 (Cl+neopentane) and 0.64 (Cl+tetramethylsilane) that are consistent with a kinematic model for the reaction in which the translational energy of the reactants is conserved into product translational energy.

PLP–LIF study of the reactions of chlorine atoms with C 2H 2, C 2H 4, and C 3H 6 in 2–100 Torr of N 2 diluent at 295 K

Pulsed laser photolysis–laser-induced fluorescence (PLP–LIF) techniques were used to study the reactions of Cl( 2P 3/2) atoms with C 2H 2 ( k 1), C 2H 4 ( k 2), and C 3H 6 ( k 3) in 2–100 Torr of N 2 diluent at 295 ± 2 K. The results are in good agreement with those from relative rate studies, improve our understanding of the pressure dependence of the title reactions, and indicate that when timescales for chlorine atom decay and regeneration are not decoupled the results from PLP–RF experiments do not provide reliable kinetic data for reactions of chlorine atoms with organic compounds.

Kinetics of the reaction of Cl atoms with CHCl 3 over the temperature range 253–313 K

The reaction CHCl 3 + Cl → CCl 3 + HCl was studied in the atmospherically relevant temperature range from 253 to 313 K and in 930 mbar of N 2 diluent using the relative rate method. A temperature dependent reaction rate constant, valid in the temperature range 220–330 K, was determined by a fit to the result of the present study and that of Orlando (1999); k = (3.77 ± 0.32) × 10 −12 exp((−1011 ± 24)/T) cm 3 molecule −1 s −1.

ChemInform Abstract: Time-resolved Infrared Absorption Measurements of Product Formation in Cl Atom Reactions with Alkenes and Alkynes

The reactions of Cl with hydrocarbons have been the subjects of study since the early days of experimental chemical kinetics. The reactions of Cl atoms with alkanes are prototypical atom abstractions; the reactions with alkenes and alkynes display a richer chemistry because of the possibility of addition to form a chlorinated hydrocarbon radical. This review discusses recent infrared absorption investigations of the reactions of Cl with unsaturated hydrocarbons, with an emphasis on deconvolution of the addition and metathesis (i.e. abstraction or addition-elimination) pathways. These experiments are described in relation to other Cl+ hydrocarbon reactions, and several examples illustrate the sensitivity of the kinetic and mechanistic behaviour of the Cl+ alkene reactions to the thermochemistry of the individual systems. In the Cl+C2H4 reaction, where metathesis is endothermic, addition dominates except at elevated temperatures or low pressures, but the exothermic metatheses of Cl with C3 unsaturated speci...

Kinetics and Mechanism of the Reaction of Methacrolein with Chlorine Atoms in 1−950 Torr of N2or N2/O2Diluent at 297 K

The rate constant of the reaction of Cl atoms with methacrolein (k(1)) has been measured relative to that of Cl with propane (k(2)) or cyclohexane (k(6)) at ambient temperature and pressures varying from 1-950 Torr. The experiments were carried out by irradiation (350 nm) of Cl(2)/methacrolein/propane or cyclohexane mixtures in N(2) or N(2)/O(2) diluent at ambient temperature in a spherical (500 cm(3)) Pyrex reactor (GC/FID analyses) or a 140 L FTIR smog chamber. The measured relative rate constant ratios in the GC/FID experiments were k(1)/k(2) = 1.464 +/- 0.015(2sigma) in N(2) and k(1)/k(2) = 1.68 +/- 0.03(2sigma) in N(2)/O(2) diluent (O(2) > 20,000 ppm). No pressure dependence was observed over the range studied in N(2) (120-950 Torr) using the GC/FID. In the FTIR/smog chamber experiments values of k(1)/k(6) = 0.645 +/- 0.032, 0.626 +/- 0.037, 0.586 +/- 0.026, and 0.479 +/- 0.024 were measured in 700, 100, 10, and 1 Torr, respectively, of N(2) diluent. Using k(2) = (1.4 +/- 0.2) x 10(-10) and k(6) = (3.3 +/- 0.5) x 10(-10) high pressure limiting rate constants of k(1) = (2.05 +/- 0.3) x 10(-10) [GC/FID] and (2.13 +/- 0.34) x 10(-10) [FTIR] cm(3) molecule(-1) s(-1) were determined. In experiments using the GC/FID reactor with N(2) diluent the following products (molar yields) were observed: 2,3-dichloro-2-methylpropanal [(47.2 +/- 8)% excluding error in calibration]; methacryloyl chloride [(22.9 +/- 2)%]; and 2-chloromethylacrolein [(2.3 +/- 0.8)%]. Addition of 200 ppm O(2) (with Cl(2) = 5000 ppm) resulted in a sharp reduction of the 2,3-dichloro-2-methylpropanal yield (to approximately 2%) with an accompanying appearance of chloroacetone [yield = (55 +/- 7)% decreasing to (44 +/- 7)% in air diluent]. The methacryloyl chloride yield was 23% for [O(2)]/[Cl(2)] ratios from 0 to 0.2 but decreased to near zero as the O(2)/Cl(2) ratio was increased to approximately 400. The variation in methacryloyl chloride yield with the O(2)/Cl(2) ratio in the initial mixture allowed an approximate measurement of the rate constant for the reaction of the methacryloyl radical with O(2) relative to that with Cl(2) (k(O(2))/k(Cl(2)) = 0.066 +/- 0.02). In experiments using the FTIR reactor in 700 Torr of N(2) diluent, methacryloyl chloride [(26 +/- 3)%] and HCl [(27 +/- 3)%] were observed as products. In 700 Torr of air diluent, the observed products were: chloroacetone [(44 +/- 5)%], CO(2) [(27 +/- 3)%], HCl [(21 +/- 3)%], and HCHO [(14 +/- 2)%], and CH(3)C(O)CH(2)OH (3-4%). The observation of CH(3)C(O)CH(2)OH indicates the presence of OH radicals in the system. At atmospheric pressure and 297 K, the title reaction proceeds [(24.5 +/- 5)%] via abstraction of the aldehydic hydrogen atom, [(2.3 +/- 0.8)%] via abstraction from the -CH(3) group, and approximately [(47 +/- 8) %] via addition to the CH(2)=C < double bond with most of the addition occurring at the terminal carbon atom (uncertainties represent statistical 2sigma). The results are discussed with respect to the literature data.

Crossed-beam dc slice imaging of chlorine atom reactions with pentane isomers

We present the first in a series of detailed investigations of the reaction of Cl atoms with hydrocarbons in crossed beams. This study focuses on reaction with the pentane isomers n-pentane, isopentane, and neopentane. These crossed-beam ion imaging experiments rely on "universal" 157 nm probe of the pentyl radical product, with dc sliced detection providing the scattering distributions directly. The results for the different target reactants were studied at two collision energies: approximately 5 and approximately 9 kcal/mol. The scattering results are quite similar for all reactants, suggesting that the nature of the abstraction site has surprisingly little influence on the dynamics. The angular distributions are broad with a backscattered peak at low collision energy and a sharp forward peak at high collision energy. The translational energy distributions are strongly coupled to the angular distributions and show, for the forward scattered products, a sharp peak at 80% of the collision energy for all reactants at both collision energies. The sideways-scattered products show the lowest fraction of energy in translation, while the backscattered translational energy distribution peaks at the lowest energy but extends to the highest, showing evidence of coupling of the internal degrees of freedom and the reaction exoergicity, into translation. The results are discussed in view of the extensive literature on related systems.

Theoretical studies of the reactions of Cl atoms with CF3CH2OCH n F(3−n) (n = 1, 2, 3)

Theoretical studies of the reactions of Cl atoms with CF3CH2OCH n F(3−n) (n = 1, 2, 3)

Reactions of chloroethenes with atomic chlorine in air at atmospheric pressure

Relative rate method at the temperature of 298 K and pressure of 1013 hPa and GC-MS detection were used for the study of kinetics of the reactions of Cl atoms with H2C=CCl2, cis-ClHC=CHCl, trans-ClHC=CHCl, ClHC=CCl2, and Cl2C=CCl2. The reaction products were identified by FTIR spectroscopy. A mechanism for the atmospheric degradation of chloro-ethenes has been suggested.