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1.
Rate constants have been determined at (298 ± 4) K for the reactions: and the relaxation processes: Time-resolved HF(1,0) emission was observed following the photolysis of F2 with pulses from an excimer laser operating on XeCl (λ = 308 nm). Analysis of the emission traces gave first-order constants for reaction and relaxation, and their dependence on [H2O] and [HCN] yielded:   相似文献   

2.
3,3-Dimethylbutanol-2 (3,3-DMB-ol-2) and 2,3-dimethylbutanol-2 (2,3-DMB-ol-2) have been decomposed in comparative-rate single-pulse shock-tube experiments. The mechanisms of the decompositions are The rate expressions are They lead to D(iC3H7? H) – D((CH3)2(OH) C? H) = 8.3 kJ and D(C2H5? H) – D(CH3(OH) CH? H) = 24.2 kJ. These data, in conjunction with reasonable assumptions, give and The rate expressions for the decomposition of 2,3-DMB-1 and 3,3-DMB-1 are and   相似文献   

3.
The reactions where Y = CH3 (M), C2H5 (E), i? C3H7 (I), and t? C4H9 (T) have been studied between 488 and 606 K. The pressures of CHD ranged from 16 to 124 torr and those of YE from 57 to 625 torr. These reactions are homogeneous and first order with respect to each reagent. The rate constants (in L/mol·s) are given by The Arrhenius parameters are used as a test for a biradical mechanism and to discuss the endo selectivity of the reactions.  相似文献   

4.
1,1,2,2-Tetramethylcyclopropane (TTMC) has been decomposed in a single-pulse shock tube. The main reaction process is Side reactions are unimportant. From comparative rate experiments (with cyclohexene decomposition as standard) the rate expression for these reactions are These numbers are consistent with a «best» value for cyclohexene decomposition of   相似文献   

5.
The thermal decomposition of butene-2-cis at low conversion and its effect on the pyrolysis of propane have been studied in the temperature range 779-812 K. It was established that 2-butene decomposes in a long-chain process, with the chain cycle (Besides the radical path, the molecular reaction can also play a role in the formation of the products.) The thermal decomposition of propane is considerably inhibited by 2-butene, which can be explained by the fact that the less reactive radicals formed in the reactions between the olefin and the chain-carrying radicals regenerate the chain cycle more slowly than the original radicals in the above chain cycle or in the reactions The reactions of the 2-propyl radical are further initiation steps. The ratios of the rate coefficients of the elementary steps of the decomposition (Table III) have been determined via the ratios of the products. Estimation of the radical concentrations indicated that only the methyl, 2-propyl and methylallyl radicals are of importance in the chain termination. On the basis of the inhibition-influenced curves, the role of the bimolecular initiation steps. could be clarified in the presence of 2-butene.  相似文献   

6.
The formation enthalpies were ascertained from the solution enthalpies in 2 n NaOH resp. 2 n NaOH + 1% H2O2. The results of equilibrium measurements in the systems give the formation enthalpies and standard entropies: . The value of the standard entropy of the gaseous MoOCl4 was estimated to be 91 (±3) cl. From the enthalpies and entropies of sublimation the values were obtained.  相似文献   

7.
Chloroethanes react with aqueous caustic to yield either elimination or substitution products. The reaction rates were measured for the dichloroethanes, trichloroethanes, tetrachloroethanes, and pentachloroethane between 283 and 353°K. The constants of HCl eleminations referring to the rate equation are given by all rate constants being in 1./mole·s and R in cal/mole· deg. With ethyl chloride, 1,1-dichloroethane, and 1,1,l-trichloroethane, the elimination is not observed and a slow substitution takes place. The influence of chlorine substituents on both sides of the molecule on mechanism and rate parameters is discussed.  相似文献   

8.
Mixtures of up to 14% azomethane in propane have been photolyzed using mainly 366 nm radiation in the ranges of 323–453 K and 25–200 torr. Detailed measurements were made of the yields of nitrogen, methane, and ethane. Other products observed were isobutane, n-butane, ethene, and propene. A detailed mechanism is proposed and shown to account for the observed variation of product yields with experimental conditions. The quantum yield of the molecular process is found to be given by the temperature-independent equation The values of rate constants obtained are where the reactions are and it is assumed that the rate constant for the reaction is given by   相似文献   

9.
The overall reaction (1) occurs readily in the gas phase, even at room temperature in the dark. The reaction is much faster than the corresponding process and does not involve the normal bromination mechanism for gas phase reactions. Reaction (1) is probably heterogeneous although other mechanisms cannot be excluded. The overall reactions (1) (2) proceed, for all practical purposes, completely to the right-hand side in the vapor phase. The expected mechanism is (3) (4) (5) (6) (7) where reaction (3) is initiated thermally or photochemically. Reaction (4) is of interest because little kinetic data are available on reactions involving abstraction of halogen by halogen and also because an accurate determination of the activation energy E4 would prmit us to calculate an acccurate value of the bond dissociation energy D(CH3? I).  相似文献   

10.
A method is described for the measurement of relative rate constants for abstraction of hydrogen from ethylene at temperatures in the region of 750 K. The method is based on the effect of the addition of small quantities of propane and isobutane on the rates of formation of products in the thermal chain reactions of ethylene. On the assumption that methane and ethane are formed by the following reactions, (1) measurements of the ratio of the rates of formation of methane and ethane in the presence and absence of the additive gave the following results: Values for k2 and k3 obtained from these ratios are compared with previous measurements.  相似文献   

11.
The kinetics of the gas phase pyrolysis of dimethyl sulfide (DMS) was studied in a static system at 681–723 K by monitoring total pressure-time behavior. Analysis showed the pressure increase to follow DMS loss. The reaction follows two concurrent paths: with a slow, minor, secondary reaction: In a seasoned reactor the reaction follows a 3/2 order rate law with rate coefficient given by with θ = 2.303 RT in kcal/mol. A free radical mechanism is proposed to account for the data and a theoretical rate coefficient is derived from independent data: which agrees well with the experimental one over the range studied. The reaction is initiated by Me2S → Me + MeS? and propagated by metathetical radical attack on Me2S. C2H4 is formed by an isomerization reaction which may in part be due to a hot radical: Thermochemical data are listed, many from estimations, for both molecular and radical species of interest in the present system.  相似文献   

12.
The kinetics of the thermal reaction between CF3OF and C3F6 have been investigated between 20 and 75°C. It is a homogeneous chain reaction of moderate length where the main product is a mixture of the two isomers 1-C3F7OCF3 (68%) and 2-C3F7OCF3 (32%). Equimolecular amounts of CF3OOF3 and C6F14 are formed in much smaller quantities. Inert gases and the reaction products have no influence on the reaction, whereas only small amounts of oxygen change the course of reaction and larger amounts produce explosions. The rate of reaction can be represented by eq. (I): The following mechanism explains the experimental results: Reaction (5) can be replaced by reactions (5a) and (5b), without changing the result: Reaction (4) is possibly a two-step reaction: For ∣CF3 = ∣C3F6∣, ν20°C = 36.8, ν50°C = 24.0, and ν70°C = 14.2.  相似文献   

13.
The reactions of O3 with CH3ONO and C2H5ONO were studied using infrared absorption spectroscopy in a static reactor at temperatures between 298 and 352K. Both reactions followed simple second-order kinetics forming the corresponding nitrate: The rate coefficients are given by .  相似文献   

14.
Cyclopentane has been decomposed in comparative-rate single-pulse shock-tube experiments. The pyrolytic mechanism involves isomerization to 1-pentene and also a minor pathway leading to cyclopropane and ethylene. This is followed by the decomposition of 1-pentene and cyclopropane. The rate expressions over the temperature range of 1000°–1200° K are Details of the cyclopentane decomposition processes are considered, and it appears that if the trimethylene radical is an intermediate, then ΔHf(trimethylene) ≤ 280 kJ/mol at 300°K.  相似文献   

15.
The flash photolysis of biacetyl produces CO, C2H6, and CH3COCH3 as main products, and in small amounts CO2, C2H4, and CH3CHO. The rate constants of reactions (2) and (3) of thermally equilibrated radicals were calculated from the amounts of products: .  相似文献   

16.
The gas-phase free radical displacement reaction has been studied in the temperature range of 240–290°C and at 140°C with the thermal decomposition of azomethane (AM) and di-tert-butylperoxide (DTBP), respectively, as methyl radical sources. The reaction products of the CD3 radicals were analyzed by mass spectrometry. Assuming negligible isotope effects, Arrhenius parameters for the elementary radical addition reaction were derived: The data are discussed with respect to the back reaction and general features of elementary addition reactions.  相似文献   

17.
The decomposition of 1-chloro-1,1-difluoroethane by a radical chain reaction has been studied in a flow reactor in the temperature range from 503 to 773 K. For the initiation of the chain small amounts of added chlorine were photolyzed with a XeCl laser (λ = 308 nm). The formation of the dehydrochlorination and chlorination products, vinylidene fluoride, and 1,2-dichloro-1,1-difluoroethane respectively, is described by a kinetic model. Arrhenius parameters for the two abstraction reactions and were determined by a competition method: Experimental and modeling results are discussed with respect to former studies on the thermal reaction of 1-chloro-1,1-difluoroethane.  相似文献   

18.
The thermal decompositions of azoethane and azoisopropane were studied in a large excess of ethylene in the temperature interval of 523–623 K. It was demonstrated that under such conditions, the bulk of the alkyl radicals react with ethylene. Via measurements on the consumption of the azo compound and on the formation of gaseous nitrogen, it was possible to determine the rate coefficients of the initiation reactions: . The resulting data were as follows: For azoethane, . For azoisopropane,   相似文献   

19.
The kinetics of the thermal bromination reaction have been studied in the range of 173–321°C. For the step we obtain where θ=2.303RT cal/mole. From the activation energy for reaction (11), we calculate that This is compared with previously published values of D(CF3?I). The relevance of the result to published work on kc for a combination of CF3 radicals is discussed.  相似文献   

20.
The thermal isomerization of cis-hexatriene (cHT) to cyclohexadiene (CHD) and the dimerization of CHD and trans-hexatriene (tHT) in the liquid phase in the temperature range 380 K-473 K are reported. The rate coefficients are: for the cHT to CHD isomerization for tHT dimerizationlog and for CHD dimerization; endo form exo form © 1993 John Wiley & Sons, Inc.  相似文献   

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