共查询到20条相似文献,搜索用时 13 毫秒
1.
Yamanaka T Kawasaki M Hurley MD Wallington TJ Schneider WF Bruce J 《Physical chemistry chemical physics : PCCP》2007,9(31):4211-4217
FTIR smog chamber techniques and ab initio calculations have been used to investigate the kinetics and mechanism of the reaction of Cl atoms with i-propanol in 700 Torr of N(2) at 296 K. The reaction is observed to proceed with a rate constant of k(1) = (8.28 +/- 0.97) x 10(-11) cm(3) molecule(-1) s(-1) and gives CH(3)C(OH)CH(3) and CH(3)CH(OH)CH(2) radicals in yields of 85 +/- 7 and 15 +/- 7%, respectively. Calculations indicate that abstraction of the secondary H can proceed through a lower energy pathway than the primary. Rapid decomposition of the chlorination product CH(3)CCl(OH)CH(3) complicates its direct detection, likely due to heterogeneous chemistry. IR spectra for the chlorides CH(3)CCl(OH)CH(3) and CH(3)CH(OH)CH(2)Cl were inferred experimentally and assignments confirmed via comparison with ab initio computed spectra. 相似文献
2.
Srikar Middala Sean Campbell Catalina Olea Austen Scruggs Alam S. Hasson 《国际化学动力学杂志》2011,43(9):507-521
The kinetics and mechanism of gas‐phase propylene oxide (PPO) reactions were studied in a 142‐L reaction chamber by long‐path Fourier transform infrared spectroscopy at atmospheric pressure and 298 K. Rate coefficients for the reaction of PPO with ozone (O3), chlorine atoms (Cl), and hydroxyl radicals (OH) were measured using the relative rate technique. Product yields of acetic acid, acetic formic anhydride, formic acid, and carbon monoxide were determined for the following reactions: PPO with Cl both in the presence and absence of NO, PPO with OH and NO, methyl acetate with Cl both in the presence and absence of NO, and ethyl formate with Cl both in the presence and absence of NO. The measured rate coefficients for PPO with O3, Cl, and OH are <3.5 × 10?21 cm3 molecule?1 s?1, (3.0 ± 0.7) × 10?11 cm3 molecule?1 s?1, and (3.0 ± 1.0) × 10?13 cm3 molecule?1 s?1, respectively. The carbon balance for the products measured ranged from 10% (for OH + PPO) to 100% (for Cl + methyl acetate in the absence of NO). The mechanistic and atmospheric implications of these measurements are discussed. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 507–521, 2011 相似文献
3.
The reaction kinetics of atomic chlorine with a series of biogenic hydrocarbons, including the two enantiomers of α‐pinene, were studied at 298 K and 1 atm pressure using a relative rate technique. The simultaneous losses of the biogenic of interest and a reference compound, either n‐nonane or n‐butane, were followed using gas chromatography with flame ionization detection as a function of the extent of photolysis of a chlorine atom precursor. Thionyl chloride, trichloroacetyl chloride or in a few trials, acetyl chloride, were photolyzed at 254 nm to generate chlorine atoms, since molecular chlorine reacted in the dark with these organics. The relative rate constants for ethane and isoprene determined relative to n‐butane using SOCl2 and CCl3COCl were compared to those determined using Cl2 to check for possible artifacts. The average relative rate constants for ethane and isoprene (both relative to n‐butane) using these new sources are (0.281 ± 0.021) and (2.49 ± 0.39) (±2 σ) respectively, within experimental error of those measured using Cl2 as the chlorine atom source. The relative rate constants averaged over all sources including Cl2 are (0.277 ± 0.025) for ethane and (2.42 ± 0.45) for isoprene. The ratios of rate constants for the chlorine atom reactions with the biogenics with formula C10H16 relative to n‐nonane were as follows: (R)‐α‐pinene (0.991 ± 0.264); (S)‐α‐pinene (0.946 ± 0.240); β‐pinene (1.09 ± 0.30); (R)‐limonene (1.33 ± 0.15); myrcene (1.36 ± 0.31); 3‐carene (1.16 ± 0.23). That for p‐cymene, C10H14, is (0.433 ± 0.072). Taking k(Cl + n‐nonane) = (4.82 ± 0.14) × 10−10 cm3 molecule−1 s−1, the absolute rate constants (in units of 10−10 cm3 molecule−1 s−1) are: (R)‐α‐pinene (4.8 ± 1.3); (S)‐α‐pinene (4.6 ± 1.2); β‐pinene (5.3 ± 1.5); limonene (6.4 ± 0.8); myrcene (6.6 ± 1.5); 3‐carene (5.6 ± 1.3); p‐cymene (2.1 ± 0.4). (All errors are ± 2 σ). Although abstraction was not measured directly in this study, it is likely a significant contributor to the overall reactions of the C10H16 biogenics. The rate constant for the reaction of the aromatic compound p‐cymene is within experimental error of that predicted from the sum of reaction with toluene plus the isopropyl substituent. A limited number of experiments for methyl vinyl ketone in N2 using CCl3COCl as the chlorine atom source and nonane as the reference compound gave a relative rate constant of (0.422 ± 0.034), corresponding to an absolute rate constant of (2.0 ± 0.2) × 10−10 cm3 molecule−1 s−1. Based on these rate constants, the lifetimes of these biogenics at dawn with respect to reaction with chlorine atoms are expected to be comparable to reaction with OH. Thus, loss of these biogenics by reaction with atomic chlorine must be taken into account in coastal regions in addition to their reactions with OH, O3 and at night, NO3. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 491–499, 1999 相似文献
4.
The trithionate-chlorine dioxide reaction has been studied spectrophotometrically in a slightly acidic medium at 25.0 ± 0.1 °C in acetate/acetic acid buffer monitoring the decay of chlorine dioxide at constant ionic strength (I = 0.5 M) adjusted by sodium perchlorate. We found that under our experimental conditions two limiting stoichiometries exist and the pH, the concentration of the reactants, and even the concentration of chloride ion affects the actual stoichiometry of the reaction that can be augmented by an appropriate linear combination of these limiting processes. It is also shown that although the formal kinetic order of trithionate is strictly one that of chlorine dioxide varies between 1 and 2, depending on the actual chlorine dioxide excess and the pH. Moreover, the otherwise sluggish chloride ion, which is also a product of the reaction, slightly accelerates the initial rate of chlorine dioxide consumption and may therefore act as an autocatalyst. In addition to that, overshoot-undershoot behavior is also observed in the [(·)ClO(2)]-time curves in the presence of chloride ion at chlorine dioxide excess. On the basis of the experiments, a 13-step kinetic model with 6 fitted kinetic parameter is proposed by nonlinear parameter estimation. 相似文献
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The kinetic and mechanism of the reaction Cl + HO2 → products (1) have been studied in the temperature range 230–360 K and at total pressure of 1 Torr of helium using the discharge‐flow mass spectrometric method. The following Arrhenius expression for the total rate constant was obtained either from the kinetics of HO2 consumption in excess of Cl atoms or from the kinetics of Cl in excess of HO2: k1 = (3.8 ± 1.2) × 10?11 exp[(40 ± 90)/T] cm3 molecule?1 s?1, where uncertainties are 95% confidence limits. The temperature‐independent value of k1 = (4.4 ± 0.6) × 10?11 cm3 molecule?1 s?1 at T = 230–360 K, which can be recommended from this study, agrees well with most recent studies and current recommendations. Both OH and ClO were detected as the products of reaction (1) and the rate constant for the channel forming these species, Cl + HO2 → OH + ClO (1b), has been determined: k1b = (8.6 ± 3.2) × 10?11 exp[?(660 ± 100)/T] cm3 molecule?1 s?1 (with k1b = (9.4 ± 1.9) × 10?12 cm3 molecule?1 s?1 at T = 298 K), where uncertainties represent 95% confidence limits. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 317–327, 2001 相似文献
7.
M. P. Sulbaek Andersen D. A. Ponomarev O. J. Nielsen M. D. Hurley T. J. Wallington 《Chemical physics letters》2001,350(5-6):423-426
Smog chamber/FTIR techniques were used to study the kinetics and mechanism of the reaction of Cl atoms with iodobenzene (C6H5I) in 20–700 Torr of N2, air, or O2 diluent at 296 K. The reaction proceeds with a rate constant k(Cl+C6H5I)=(3.3±0.7)×10−11 cm3 molecule−1 s−1 to give chlorobenzene (C6H5Cl) in a yield which is indistinguishable from 100%. The title reaction proceeds via a displacement mechanism (probably addition followed by elimination). 相似文献
8.
Oxygen atoms are detected by NO + O + M chemiluminescence as a secondary product of the reaction between Cl and O3. The mechanism Cl + O3 → ClO + O2(1Σ+g), O2(1Σ+g) + O3 → O2 + O2 + O is proposed to account for the oxygen atom formation. The branching ratio to the O2(1Σ+g) product in the reaction of Cl with O3 is estimated to be in the range (0.1–0.5) x 10?2. 相似文献
9.
Lai‐Cai Li Jing Wang Xin Wang An‐Min Tian Ning‐Bew Wong 《International journal of quantum chemistry》2002,87(5):288-292
Ab initio calculations of the potential energy surface for the F + O3 and Cl + O3 reactions have been performed using the G3 and G3MP2 methods, which optimize the geometry configuration of reactants, products, intermediates, and transition states. The results show that fluorine atoms react with ozone as violently as chlorine atoms. At the same time, we have studied the reaction mechanisms of F atoms and Cl atoms with methane. It is found that fluorine atoms prefer to react with methane and chlorine atoms with ozone when there is competition between ozone and methane. Therefore, we can reasonably explain why chlorine atoms play the main role of reactants depleting ozone, while the more active fluorine atoms deplete less ozone. © 2002 Wiley Periodicals, Inc.; DOI 10.1002/qua.10119 相似文献
10.
The reaction of atomic chlorine with neopentane was studied in the gas phase with the Very Low Pressure Reactor (VLPR) technique over the temperature range 273–333 K. The absolute reaction rate was found to be temperature-independent, and the average rate constant was k1 = (1.11± 0.13) × 10?10 cm3 molecule?1 s?1 within experimental error. The reaction proceeds via metathesis of a hydrogen atom with no activation energy, and leads to the formation of HCl and neopentyl radical. © 1995 John Wiley & Sons, Inc. 相似文献
11.
Zhao Z Huskey DT Olsen KJ Nicovich JM McKee ML Wine PH 《Physical chemistry chemical physics : PCCP》2007,9(31):4383-4394
A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the reaction of atomic chlorine with pyridine (C(5)H(5)N) as a function of temperature (215-435 K) and pressure (25-250 Torr) in nitrogen bath gas. At T> or = 299 K, measured rate coefficients are pressure independent and a significant H/D kinetic isotope effect is observed, suggesting that hydrogen abstraction is the dominant reaction pathway. The following Arrhenius expression adequately describes all kinetic data at 299-435 K for C(5)H(5)N: k(1a) = (2.08 +/- 0.47) x 10(-11) exp[-(1410 +/- 80)/T] cm(3) molecule(-1) s(-1) (uncertainties are 2sigma, precision only). At 216 K < or =T< or = 270 K, measured rate coefficients are pressure dependent and are much faster than computed from the above Arrhenius expression for the H-abstraction pathway, suggesting that the dominant reaction pathway at low temperature is formation of a stable adduct. Over the ranges of temperature, pressure, and pyridine concentration investigated, the adduct undergoes dissociation on the time scale of our experiments (10(-5)-10(-2) s) and establishes an equilibrium with Cl and pyridine. Equilibrium constants for adduct formation and dissociation are determined from the forward and reverse rate coefficients. Second- and third-law analyses of the equilibrium data lead to the following thermochemical parameters for the addition reaction: Delta(r)H = -47.2 +/- 2.8 kJ mol(-1), Delta(r)H = -46.7 +/- 3.2 kJ mol(-1), and Delta(r)S = -98.7 +/- 6.5 J mol(-1) K(-1). The enthalpy changes derived from our data are in good agreement with ab initio calculations reported in the literature (which suggest that the adduct structure is planar and involves formation of an N-Cl sigma-bond). In conjunction with the well-known heats of formation of atomic chlorine and pyridine, the above Delta(r)H values lead to the following heats of formation for C(5)H(5)N-Cl at 298 K and 0 K: Delta(f)H = 216.0 +/- 4.1 kJ mol(-1), Delta(f)H = 233.4 +/- 4.6 kJ mol(-1). Addition of Cl to pyridine could be an important atmospheric loss process for pyridine if the C(5)H(5)N-Cl product is chemically degraded by processes that do not regenerate pyridine with high yield. 相似文献
12.
The kinetics and mechanism of the reaction of chlorine atoms with n‐butanal and n‐pentanal have been investigated in a 142‐L reaction cell coupled to a Fourier transform infrared (FTIR) spectrometer at 298 ± 2 K and at 800 ± 3 Torr. The rate coefficients for Cl + n‐butanal and Cl + n‐pentanal were measured using the relative rate technique with isopropanol and ethene as the reference compounds. The yield of acyl radicals was determined by measuring yields of acid chloride and carbon monoxide products from the reaction of Cl + aldehyde in the absence of oxygen. The rate coefficients for Cl + n‐butanal and Cl + n‐pentanal are (1.63 ± 0.59) × 10?10 cm3 molecule?1 s? 1 and (2.37 ± 0.82) × 10?10 cm3 molecule?1 s?1, respectively. The yields of acyl radicals from the reactions are 0.66 ± 0.04 for n‐butanal and 0.45 ± 0.04 for n‐pentanal. Under ambient conditions, the acyl radicals generated will react almost exclusively with oxygen. Mechanistic implications of these measurements are discussed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 133–141, 2009 相似文献
13.
The use of iodine monochloride (ICl) as a thermal source of chlorine atoms in known concentration is discussed with particular reference to the suppression, by large excesses of iodine, of the chain processes normally associated with chlorine atom reactions. The kinetics and mechanism of the reaction of ICl with hydrogen are presented in a study covering the temperature range 205–337°C, and the pressure ranges: ICl, 6–20 torr; I2, 3–13 torr; and H2, 9–520 torr. The reaction, followed spectrophotometrically in a static system, is shown to be homogeneous, first order in ICl and in H2, and inverse half-order in I2, over several half-lifetimes of the ICl, yielding HCl as the sole product. The rate data obtained in this work for the reaction are combined with the critically evaluated results of other workers in an Arrhenius plot covering the temperature range 286–730°C, and three orders-of-magnitude in the rate constant, yielding the results, log k1/(1/mole sec) = 10.68–5.26/θ, where θ = 2.303RT in kcal/mole. This value of k1 is lower by a factor of about two than that proposed in a recent review by Fettis and Knox, and is clearly at variance by a factor of two or more with the most recent data of Clyne and Stedman. 相似文献
14.
T. J. Wallington J. C. Ball A. M. Straccia M. D. Hurley E. W. Kaiser M. Dill W. F. Schneider M. Bilde 《国际化学动力学杂志》1996,28(8):627-635
The kinetics and mechanism of the gas-phase reaction of Cl atoms with CH2CO have been studied with a FTIR spectrometer/smog chamber apparatus. Using relative rate methods the rate of reaction of Cl atoms with ketene was found to be independent of total pressure over the range 1–700 torr of air diluent with a rate constant of (2.7 ± 0.5) × 10−10 cm3 molecule−1 s−1 at 295 K. The reaction proceeds via an addition mechanism to give a chloroacetyl radical (CH2ClCO) which has a high degree of internal excitation and undergoes rapid unimolecular decomposition to give a CH2Cl radical and CO. Chloroacetyl radicals were also produced by the reaction of Cl atoms with CH2ClCHO; no decomposition was observed in this case. The rates of addition reactions are usually pressure dependent with the rate increasing with pressure reflecting increased collisional stabilization of the adduct. The absence of such behavior in the reaction of Cl atoms with CH2CO combined with the fact that the reaction rate is close to the gas kinetic limit is attributed to preferential decomposition of excited CH2ClCO radicals to CH2Cl radicals and CO as products as opposed to decomposition to reform the reactants. As part of this work ab initio quantum mechanical calculations (MP2/6-31G(d,p)) were used to derive ΔfH298(CH2ClCO) = −(5.4 ± 4.0) kcal mol−1. © 1996 John Wiley & Sons, Inc. 相似文献
15.
The kinetics of the reaction of O(3P) atoms with acetone were investigated using fast flow methods. The reaction was studied over a temperature range of 298 to 478°K. The specific rate constant obtained was (1.9 ± 0.4) × 1012 exp(—5040 ± 180/1.987 T) cm3/mol·sec. The observation of a sizable primary H/D kinetic isotope effect in comparing rates of CH3COCH3 and CD3COCD3 led to the conclusion that the major reaction channel involves H atom abstraction, namely, The rather low Arrhenius preexponential factor obtained in this reaction is compared and contrasted with those reported for other reactions of O(3P) with low molecular weight compounds. 相似文献
16.
Nicovich JM Parthasarathy S Pope FD Pegus AT McKee ML Wine PH 《The journal of physical chemistry. A》2006,110(21):6874-6885
A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the reaction of chlorine atoms with dimethyl sulfoxide (CH3S(O)CH3; DMSO) as a function of temperature (270-571 K) and pressure (5-500 Torr) in nitrogen bath gas. At T = 296 K and P > or = 5 Torr, measured rate coefficients increase with increasing pressure. Combining our data with literature values for low-pressure rate coefficients (0.5-3 Torr He) leads to a rate coefficient for the pressure independent H-transfer channel of k1a = 1.45 x 10(-11) cm3 molecule(-1) s(-1) and the following falloff parameters for the pressure-dependent addition channel in N2 bath gas: k(1b,0) = 2.53 x 10(-28) cm6 molecule(-2) s(-1); k(1b,infinity) = 1.17 x 10(-10) cm3 molecule(-1) s(-1), F(c) = 0.503. At the 95% confidence level, both k1a and k1b(P) have estimated accuracies of +/-30%. At T > 430 K, where adduct decomposition is fast enough that only the H-transfer pathway is important, measured rate coefficients are independent of pressure (30-100 Torr N2) and increase with increasing temperature. The following Arrhenius expression adequately describes the temperature dependence of the rate coefficients measured at over the range 438-571 K: k1a = (4.6 +/- 0.4) x 10(-11) exp[-(472 +/- 40)/T) cm3 molecule(-1) s(-1) (uncertainties are 2sigma, precision only). When our data at T > 430 K are combined with values for k1a at temperatures of 273-335 K that are obtained by correcting reported low-pressure rate coefficients from discharge flow studies to remove the contribution from the pressure-dependent channel, the following modified Arrhenius expression best describes the derived temperature dependence: k1a = 1.34 x 10(-15)T(1.40) exp(+383/T) cm3 molecule(-1) s(-1) (273 K < or = T < or = 571 K). At temperatures around 330 K, reversible addition is observed, thus allowing equilibrium constants for Cl-DMSO formation and dissociation to be determined. A third-law analysis of the equilibrium data using structural information obtained from electronic structure calculations leads to the following thermochemical parameters for the association reaction: delta(r)H(o)298 = -72.8 +/- 2.9 kJ mol(-1), deltaH(o)0 = -71.5 +/- 3.3 kJ mol(-1), and delta(r)S(o)298 = -110.6 +/- 4.0 J K(-1) mol(-1). In conjunction with standard enthalpies of formation of Cl and DMSO taken from the literature, the above values for delta(r)H(o) lead to the following values for the standard enthalpy of formation of Cl-DMSO: delta(f)H(o)298 = -102.7 +/- 4.9 kJ mol(-1) and delta(r)H(o)0 = -84.4 +/- 5.8 kJ mol(-1). Uncertainties in the above thermochemical parameters represent estimated accuracy at the 95% confidence level. In agreement with one published theoretical study, electronic structure calculations using density functional theory and G3B3 theory reproduce the experimental adduct bond strength quite well. 相似文献
17.
A. M. Efremov A. V. Yudina D. B. Murin O. S. Dement’ev V. I. Svettsov 《High Energy Chemistry》2013,47(2):57-61
The mechanisms of the influence of the initial composition of an HCl-Ar mixture on the kinetics and concentration of chlorine atoms in direct-current glow discharge plasma have been studied. It has been found that an increase in the Ar content at a constant total gas pressure leads to an increase in the degree of dissociation of HCl due to an increase in the electron impact dissociation efficiency. 相似文献
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The kinetics of the reactions of F and C1 atoms with ethylene oxide have been studied using relative rate techniques in 10–700 Torr of either nitrogen or air diluent at 295 ± 2 K; k(F + C2H4O) = (9.4 ± 1.6) × 10?11 and k(C1 + C2H4O) = (5.0 ± 0.9) × 10?12 cm3 molecule?1 s?1. The result for k(F + C2H4O) is in good agreement with the literature data. The result for k(C1 + C2H4O) is a factor of 5.6 lower than that reported previously. It seems likely that in the previous study most of the loss of C2H4O attributed to reaction with C1 atoms was actually caused by unwanted secondary reactions leading to an overestimate of k(C1 + C2H4O). © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 122–125, 2002 相似文献
20.
Manolis N. Romanias Vassileios G. Stefanopoulos Dimitrios K. Papanastasiou Vassileios C. Papadimitriou Panos Papagiannakopoulos 《国际化学动力学杂志》2010,42(12):724-734
The 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 相似文献