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1.
The reactions of ground-state oxygen atoms with carbonothioicdichloride, carbonothioicdifluoride, and tetrafluoro-1,3-dithietane have been studied in a crossed molecular jet reactor in order to determine the initial reaction products and in a fast-flow reactor in order to determine their overall rate constants at temperatures between 250 and 500 K. These rate constants are??(O + C2CS) =(3.09 ± 0.54) × 10?11 exp(+115 ± 106 cal/mol/RT),??(O + F2CS) = (1.22 ± 0.19) × 10?11 exp(-747 ± 95 cal/mol/RT), and??(O + F4C2S2) = (2.36 ± 0.52) × 10?11 exp(-1700 ± 128 cal/mol/RT) cm3/molec˙sec. The detected reaction products and their rate constants indicate that the primary reaction mechanism is the electrophilic addition of the oxygen atom to the sulfur atom contained in the reactant molecule to form an energy-rich adduct which then decomposes by C-S bond cleavage. 相似文献
2.
Absolute rate constants are measured for the reactions: OH + CH2O, over the temperature range 296–576 K and for OH + 1,3,5-trioxane over the range 292–597 K. The technique employed is laser photolysis of H2O2 or HNO3 to produce OH, and laser-induced fluorescence to directly monitor the relative OH concentration. The results fit the following Arrhenius equations: k (CH2O) = (1.66 ± 0.20) × 10?11 exp[?(170 ± 80)/RT] cm3 s?1 and k(1,3,5-trioxane) = (1.36 ± 0.20) × 10?11 exp[?(460 ± 100)/RT] cm3 s?1. The transition-state theory is employed to model the OH + CH2O reaction and extrapolate into the combustion regime. The calculated result covering 300 to 2500 K can be represented by the equation: k(CH2O) = 1.2 × 10?18 T2.46 exp(970/RT) cm3 s?1. An estimate of 91 ± 2 kcal/mol is obtained for the first C? H bond in 1,3,5-trioxane by using a correlation of C? H bond strength with measured activation energies. 相似文献
3.
E. W. Kaiser 《国际化学动力学杂志》1993,25(8):667-680
Relative rate experiments using UV photolysis of F2 or Cl2 have been used to determine rate constant ratios for several hydrofluorocarbon (HFC) reactions with Cl or F atoms and for HFC alkyl radicals with molecular halogens. For mixtures with F2 present, dark reactions are, also, observed which are attributed to thermal dissociation of the F2 to form F atoms. At 296 K, the rate of reaction (1a) [CF2HCH3 + F → CF2CH3 + HF] relative to (1b) [CF2HCH3 + F → CF2HCH2 + HF] is k1a/k1b = 0.73 (±0.13) and is independent of T (= 262–348 K). At 296 K, the ratio of reaction (2a) [CF2HCH2F + F → products] to that of (k1a + k1b) is (k1a + k1b)/k2a = 2.7 (±0.4), and for reaction (2b) [CF3CH3 + F → products] (k1a + k1b)/k2b = 22 ± 12. The temperature dependence (263–365 K) of the rate constant of reaction (3) [CF3CFH2 + Cl → products] relative to reaction (4) [CF3CFClH + Cl → products] is k3/k4(±10%) = 1.55 exp(?300 K/T). For the alkyl radicals formed from HFC 152a (CF2HCH2 and CF2CH3) and from HFC 134a (CF3CFH), rate constants for the reactions with F2 and Cl2 were measured relative to their reactions with O2. The rate constant of reaction (5cl) [CF2CH3 + Cl2 → CF2ClCH3 + Cl] relative to (5o) [CF2CH3 + O2 → CF2(O2)CH3] is k5cl/k5o(±15%) = 0.3 exp(200 K/T). For reaction (5f) [CF2CH3 + F2 → CF3CH3 + F], k5f/k5o(±35%) = 0.23. The ratio for reaction (6f) [CF2HCH2 + F2 → CF2HCH2F + F] relative to (6o) [CF2HCH2 + O2 → CF2HCH2O2] is k6f/k6o(±40%) = 1.23 exp(?730 K/T). The rate constant ratio for reaction (8cl) [CF3CFH + Cl2 → CF3CFClH + Cl] relative to reaction (8o) [CF3CFH + O2 → CF3CFHO2] is k8cl/k8o(±18%) = 0.16 exp(?940 K/T). For reaction (8f) [CF3CFH + F2 → CF3CF2H + F], k8f/k8o(±35%) = 0.6 exp(?860 K/T). © 1993 John Wiley & Sons, Inc. 相似文献
4.
High-temperature (>1000°K) pyrolysis of acetaldehyde (~1% in an atmosphere of pure nitrogen) was examined in a turbulent flow reactor which permits accurate determination of the spatial distribution of the stable species. Results show that the products in order of decreasing importance are CO, CH4, H2, C2H6, and C2H4. Rates of formation were consistent with the Rice–Herzfeld mechanism by including reactions to explain C2H4 formation and the possible presence of ketene. A steady-state treatment of the complete mechanism indicates that the overall reaction order decreases from \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{3}{2} $\end{document} to 1, which is supported by the new experimental data. Using earlier low-temperature results, the rate constant for the reaction CH3CHO → CH3 + CHO (1) was found as k1=1015.85±0.21 exp (?81,775±1000/RT) sec?1. Also, data for the ratio of rate constants for reactions CH3CHO + CH3 → CH4 + CH3CO (4) and 2CH3 → C2H6(6) were fitted to the empirical expression k4/k61/2=10?13.89±0.03T6.1 exp(?1720±70/RT) (cm3/mole·sec)1/2 and causes for the curvature are discussed. The noncatalytic effect of oxygen on acetaldehyde pyrolysis at high temperature is explained. 相似文献
5.
E. S. Vasil’ev I. I. Morozov W. Hack K. -H. Hoyermann M. Hold 《Kinetics and Catalysis》2006,47(6):834-845
Gas-phase reactions typical of the Earth’s atmosphere have been studied for a number of partially fluorinated alcohols (PFAs). The rate constants of the reactions of CF3CH2OH, CH2FCH2OH, and CHF2CH2OH with fluorine atoms have been determined by the relative measurement method. The rate constant for CF3CH2OH has been measured in the temperature range 258–358 K (k = (3.4 ± 2.0) × 1013exp(?E/RT) cm3 mol?1 s?1, where E = ?(1.5 ± 1.3) kJ/mol). The rate constants for CH2FCH2OH and CHF2CH2OH have been determined at room temperature to be (8.3 ± 2.9) × 1013 (T = 295 K) and (6.4 ± 0.6) × 1013 (T = 296 K) cm3 mol?1 s?1, respectively. The rate constants of the reactions between dioxygen and primary radicals resulting from PFA + F reactions have been determined by the relative measurement method. The reaction between O2 and the radicals of the general formula C2H2F3O (CF3CH2? and CF3?HOH) have been investigated in the temperature range 258–358 K to obtain k = (3.8 ± 2.0) × 108exp(?E/RT) cm3 mol?1 s?1, where E = ?(10.2 ± 1.5) kJ/mol. For the reaction between O2 and the radicals of the general formula C2H4FO (? HFCH2O, CH2F?HOH, and CH2FCH2?) at T = 258–358 K, k = (1.3 ± 0.6) × 1011exp(?E/RT) cm3 mol?1 s?1, where E = ?(5.3 ± 1.4) kJ/mol. The rate constant of the reaction between O2 and the radicals with the general formula C2H3F2O (?F2CH2O, CHF2?HOH, and CHF2CH2?) at T = 300 K is k = 1.32 × 1011 cm3 mol?1 s?1. For the reaction between NO and the primary radicals with the general formula C2H2F3O (CF3CH2? and CF3?HOH), which result from the reaction CF3CH2OH + F, the rate constant at 298 K is k = 9.7 × 109 cm3 mol?1 s?1. The experiments were carried out in a flow reactor, and the reaction mixture was analyzed mass-spectrometrically. A mechanism based on the results of our studies and on the literature data has been suggested for the atmospheric degradation of PFAs. 相似文献
6.
The kinetics of the reactions of hydroxy radicals with cyclopropane and cyclobutane has been investigated in the temperature range of 298–492 K with laser flash photolysis/resonance fluorescence technique. The temperature dependence of the rate constants is given by k1 = (1.17 ± 0.15) × 10?16 T3/2 exp[?(1037 ± 87) kcal mol?1/RT] cm3 molecule?1 s1 and k2 = (5.06 ± 0.57) × 10?16 T3/2 exp[?(228 ± 78) kcal mol?1/RT] cm3 molecule?1 s?1 for the reactions OH + cyclopropane → products (1) and OH + cyclobutane → products (2), respectively. Kinetic data available for OH + cycloalkane reactions were analyzed in terms of structure-reactivity correlations involving kinetic and energetic parameters. 相似文献
7.
Using the relative kinetic method, rate coefficients have been determined for the gas‐phase reactions of chlorine atoms with propane, n‐butane, and isobutane at total pressure of 100 Torr and the temperature range of 295–469 K. The Cl2 photolysis (λ = 420 nm) was used to generate Cl atoms in the presence of ethane as the reference compound. The experiments have been carried out using GC product analysis and the following rate constant expressions (in cm3 molecule?1 s?1) have been derived: (7.4 ± 0.2) × 10?11 exp [‐(70 ± 11)/ T], Cl + C3H8 → HCl + CH3CH2CH2; (5.1 ± 0.5) × 10?11 exp [(104 ± 32)/ T], Cl + C3H8 → HCl + CH3CHCH3; (7.3 ± 0.2) × 10?11 exp[?(68 ± 10)/ T], Cl + n‐C4H10 → HCl + CH3 CH2CH2CH2; (9.9 ± 2.2) × 10?11 exp[(106 ± 75)/ T], Cl + n‐C4H10 → HCl + CH3CH2CHCH3; (13.0 ± 1.8) × 10?11 exp[?(104 ± 50)/ T], Cl + i‐C4H10 → HCl + CH3CHCH3CH2; (2.9 ± 0.5) × 10?11 exp[(155 ± 58)/ T], Cl + i‐C4H10 → HCl + CH3CCH3CH3 (all error bars are ± 2σ precision). These studies provide a set of reaction rate constants allowing to determine the contribution of competing hydrogen abstractions from primary, secondary, or tertiary carbon atom in alkane molecule. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 651–658, 2002 相似文献
8.
Measurements of the NO-catalyzed dissociation of I2 in Ar in incident shock waves were carried out in the temperature range of 700°-1520°K and at total concentrations of 5 × 10?6-6 × 10?5 mol/cm3, using ultraviolet-visible absorption techniques to monitor the disappearance of I2. It was shown that the main reaction responsible for the disappearance under these conditions is I2 + NO → INO + I, for which a rate coefficient of (2.9 ± 0.5) × 1013 exp[-(18.0 ± 0.6 kcal/mol)/RT] cm2/mol·sec was determined. The INO formed dissociates rapidly in a subsequent reaction. The reaction, therefore, constitutes a “chemical model” for a “thermal collisional release mechanism.” Preliminary measurements of the rate coefficient for I2 + NO2 → INO2 + I are also presented. Combined with information on the reverse reactions obtained in earlier room temperature experiments, these results lead to accurate values of ΔH°f for INO and INO2 equal to 29.7 ± 0.5 and 15.9 ± 1 kcal/mol, respectively. 相似文献
9.
Reactions of ozone with simple olefins have been studied between 6 and 800 mtorr total pressure in a 220-m3 reactor. Rate constants for the removal of ozone by an excess of olefin in the presence of 150 mtorr oxygen were determined over the temperature range 280 to 360° K by continuous optical absorption measurements at 2537 Å. The technique was tested by measuring the rate constants k1 and k2 of the reactions (1) NO + O3 → NO2 + O2 and (2) NO2 + O3 rarr; NO3 + O2 which are known from the literature. The results for NO, NO2, C2H4, C3H6, 2-butene (mixture of the isomers), 1,3→butadiene, isobutene, and 1,1 -difluoro-ethylene are 1.7 × 10?1 4 (290°K), 3.24 × 10?17 (289°K), 1.2 × 10?1 4 exp (–4.95 ± 0.20/RT), 1.1 × 10?1 4 exp (–3.91 ± 0.20/RT), 0.94 × 10?1 4 exp ( –2.28 ± 0.15/RT), 5.45 ± 10?1 4 exp ( –5.33 ± 0.20/RT), 1.8 ×10?17 (283°K), and 8 × 10?20 cm3/molecule ·s(290°K). Productformation from the ozone–propylene reaction was studied by a mass spectrometric technique. The stoichiometry of the reaction is near unity in the presence of molecular oxygen. 相似文献
10.
《国际化学动力学杂志》2018,50(6):425-434
Reactions of F2 molecules exhibit unusual features, manifesting in high reactivity of F2 with respect to some closed‐shell molecules and low reactivity toward chemically active species, such as halogen and oxygen atoms. The existing data base on the reactions of F2 being rather sparse, kinetic and mechanistic studies (preferably over a wide temperature range) are needed to better understand the nature of the specific reactivity of fluorine molecule. In the present work, reactions of F2 with Br atoms and Br2 have been studied for the first time in an extended temperature range using a discharge flow reactor combined with an electron impact ionization mass spectrometer. The rate constant of the reaction F2 + Br → F +BrF (1) was determined either from kinetics of the reaction product, BrF, formation or from the kinetics of Br consumption in excess of F2: k1 = (4.66 ± 0.93) × 10−11 exp(−(4584 ± 86)/T) cm3 molecule−1 s−1 at T = 300–940 K. The rate constant of the reaction F2 + Br2 → products (2), k2 = (9.23 ± 2.68) × 10−11 exp(−(8373 ± 194)/T) cm3 molecule−1 s−1, was determined in the temperature range 500–958 K by monitoring both reaction product (FBr) formation and F2 consumption kinetics in excess of Br2. The results of the experimental measurements of the yield of FBr (1.02 ± 0.07 at T = 960 K) combined with thermochemical calculations indicate that F+Br2F forming channel of reaction (2) is probably the dominant one, at least, at highest temperature of the study. 相似文献
11.
The rate constants of the gas-phase reactions of the chromium atom with CC14, CHC13, and CH2Cl2 were measured behind shock waves at 800–1400 K. The results are presented in the Arrhenius form (the activation energy is
given in kJ/mol):k
CCl
4 = 1014.32±0.36exp[-(2.0±7.5)/RT],k
CHCl
3 = 1014.72±0.21exp[-(18.5.±4.0)/RT, andk
CH
2
Cl
2> = 1014.33±0.16exp[-(24.1±3.1)/RT]cm3mol-1s-1. 相似文献
12.
The kinetics of the reaction of O + CH3OCH3 were investigated using fast-flow apparatus equipped with ESR and mass-spectrometric detection. The concentration of O(3P) atoms to CH3OCH3 was varied over an unusually large range. The rate constant for reaction was found to be k = (5.0 ± 1.0) × 1012 exp [(?2850 ± 200/RT)] cm3 mole?1 sec?1. The reaction O + CH3OH was studied using ESR detection. Based on an assumed stoichiometry of two oxygen atoms consumed per molecule of CH3OH which reacts, we obtain a value of k = (1.70 ± 0.66) × 1012 exp [(?2,280 ± 200/RT)] cm3 mole?1 sec?1 for the reaction The results obtained in this study are compared with the results from other workers on these reactions. The observation of essentially equal activation energies in these two reactions is indicative of approximately equal C? H bond strengths in CH3OCH3 and CH3OH. This is in agreement with recent measurements of these bond energies. 相似文献
13.
Yoshiaki Hidaka Takuji Nakamura Hiroya Tanaka Koji Inami Hiroyuki Kawano 《国际化学动力学杂志》1990,22(7):701-709
The pyrolysis of 2% CH4 and 5% CH4 diluted with Ar was studied using both a single–pulse and time–resolved spectroscopic methods over the temperature range 1400–2200 K and pressure range 2.3–3.7 atm. The rate constant expressions for dissociative recombination reactions of methyl radicals, CH3 + CH3 → C2H5 + H and CH3 + CH3 → C2H4 + H2, and for C3H4 formation reaction were investigated. The simulation results required considerably lower value than that reported for CH3 + CH3 → C2H4 + H2. Propyne formation was interpreted well by reaction C2H2 + CH3 → P-C3H4 + H with ?? = 6.2 × 1012 exp(?17 kcal/RT) cm3 mol?1 s?1. 相似文献
14.
The reactions of hydrogen atoms produced by the mercury-photosensitized decomposition of H2 with bis(trifluoromethyl)disulfide has been studied. The rate coefficient for the primary reaction, H + CF3SSCF3 → CF3SH + CF3S, was determined in competition with the reaction H + C2H4S → SH + C2H4 to have the value k = (3.0 ± 0.18) × 1014 exp[-(4560 ± 140)/RT] cm3 mol?1 S?1. The high A factor can be partially accounted for by assuming free rotation for the two CF3 groups and the SCF3 groups about the S—S bond in the transition state. The relatively high activation energy is attributed to inductive and orbital overlap effects. CH3SH, H2S, and CF3SH all react with CF3SSCF3 to yield solid complexes which were not explored further. 相似文献
15.
The reaction of atomic hydrogen with O2(1Δg) has been investigated as a function of temperature, using a fast discharge-flow apparatus equipped for EPR detection of free radical species. The rate constant for the overall reaction was measured as (1.46 ± 0.49) × 10?11 exp(-4000 ± 200 cal/mol/RT) cm3/s. Evidence is presented which suggests that the reaction occurs principally via abstraction, H + O2(1Δg) → OH + O, rather than via physical quenching, H + O2(1Δg) → H + O2(X3Σg?). 相似文献
16.
The thermal decomposition of propane was studied behind reflected shock waves over the temperature range 1100–1450 K and the pressure range 1.5–2.6 atm, by both monitoring the time variations of absorption at 3.39 μm and analyzing the concentrations of the reacted gas mixtures. The rate constants of the elementary reactions were discussed from the results. The rate constant expressions, k1 = 1.1 × 1016 exp (?84 kcal/RT) s?1 and k4 = 9.3 × 1013 exp(?8 kcal/RT) cm3 mol?1 s?1, of reactions C3H8 → CH3 + C2H5 and C3H8 + H → n-C3H7 + H2 were evaluated, respectively. 相似文献
17.
By allowing dimethyl peroxide (10?4M) to decompose in the presence of nitric oxide (4.5 × 10?5M), nitrogen dioxide (6.5 × 10?5M) and carbon tetrafluoride (500 Torr), it has been shown that the ratio k2/k2′ = 2.03 ± 0.47: CH3O + NO → CH3ONO (reaction 2) and CH3O + NO2 → CH3ONO2 (reaction 2′). Deviations from this value in this and previous work is ascribed to the pressure dependence of both these reactions and heterogeneity in reaction (2). In contrast no heterogeneous effects were found for reaction (2′) making it an ideal reference reaction for studying other reactions of the methoxy radical. We conclude that the ratio k2/k2′ is independent of temperature and from k1 = 1010.2±0.4M?1 sec?1 we calculate that k2′ = 109.9±0.4M?1 sec?1. Both k2 and k2′ are pressure dependent but have reached their limiting high-pressure values in the presence of 500 Torr of carbon tetrafluoride. Preliminary results show that k4 = 10.9.0±0.6 10?4.5±1.1/ΘM?1 sec?1 (Θ = 2.303RT kcal mole?1) and by k4 = 108.6±0.6 10?2.4±1.1/ΘM?1 sec?1: CH3O + O2 → CH2O + HO2 (reaction 4) and CH3O + t-BuH → CH3OH + (t-Bu) (reaction 4′). 相似文献
18.
Kinetics and mechanisms for the reactions of HNO with CH3 and C6H5 have been investigated by ab initio molecular orbital (MO) and transition‐state theory (TST) and/or Rice‐Ramsperger‐Kassel‐Marcus/Master Equation (RRKM/ME) calculations. The G2M(RCC, MP2)//B3LYP/6‐31G(d) method was employed to evaluate the energetics for construction of their potential energy surfaces and prediction of reaction rate constants. The reactions R + HNO (R = CH3 and C6H5) were found to proceed by two key product channels giving (1) RH + NO and (2) RNO + H, primarily by direct abstraction and indirect association/decomposition mechanisms, respectively. As both reactions initially occur barrierlessly, their rate constants were evaluated with a canonical variational approach in our TST and RRKM/ME calculations. For practical applications, the rate constants evaluated for the atmospheric‐pressure condition are represented by modified Arrhenius equations in units of cm3 mol?1 s?1 for the temperature range 298–2500 K: κ1A = 1.47 × 1011 T 0.76 exp[?175/ T ], κ2A = 8.06 × 103 T 2.40 exp[?3100/ T ], κ1B = 3.78 × 105 T 2.28 exp[230/ T ], and κ2B = 3.79 × 109 T 1.19 exp[?4800/ T ], where A and B represent CH3 and C6H5 reactions, respectively. Based on the predicted rate constant at 1 atm pressure for R + HNO → RNO + H, we estimated their reverse rate constants for R + HNO production from H + RNO in units of cm3 mol?1 s?1: κ?2A′ = 7.01 × 1010 T 0.84 exp[120/ T ] and κ?2B′ = 2.22 × 1019 T ?1.01 exp[?9700/ T ]. The heats of formation at 0 K for CH3NO, CH3N(H)O, CH3NOH, C6H5N(H)O, and C6H5NOH have been estimated to be 18.6, 18.1, 22.5, 47.2, and 50.7 kcal mol?1 with an estimated ±1 kcal mol?1 error. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 261–274, 2005 相似文献
19.
M. B. Colket 《国际化学动力学杂志》1984,16(4):353-369
The reaction chemistry of C2N2? Ar and C2N2? NO? Ar mixtures has been investigated behind incident shock waves. Progress of the reaction was monitored by observing the cyano radical (CN) in absorption at 388.3 nm. A quantitative spectroscopic model was used to determine concentration histories of CN. From initial slopes of CN concentration during cyanogen pyrolysis, the rate constant for C2N2 + M → 2CN + M (1) was determined to be k1 = (4.11 ± 1.8) × 1016 exp(?47,070 ± 1400/T) cm3/mol · s. A reaction sequence for the C2N2? NO system was developed, and CN profiles were computed. By comparison with experimental CN profiles the rate constant for the reaction CN + NO → NCO + N (3) was determined to be k3 = 10(14.0 ± 0.3) exp(?21,190 ± 1500/T) cm3/mol · s. In addition, the rate of the four-centered reaction CN + NO → N2 + CO (2) was estimated to be approximately three orders of magnitude below collision frequency. 相似文献
20.
A fast-flow apparatus with mass spectrometric detection was used to study the system F + CHFO between 2 and 3.5 mbar total pressure. The rate constant of the primary reaction was evaluated directly to yield at 298 K k(1) = (8.8 ± 1.4) * 10?13 cm3 * molecule?1 * s?1. Numerical modelling was used to determine the rate constant at 298 K of the subsequent reaction CFO + CFO → CF2O + CO: k(2) = (4.9 ± 2.0) * 10?11 cm3 * molecule?1 * s?1. The possible occurrences of secondary reactions, CFO + F + M → CF2O + M, and CFO + F2 → CF2O + F, can be excluded under the present conditions. © 1993 John Wiley & Sons, Inc. 相似文献