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
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
The kinetics of the gamma-radiation-induced free radical chain reaction in solutions of C2Cl3F in cyclohexane (RH) was investigated over a temperature range of 87.5–200°C. The following rate constants and rate constant ratios were determined for the reactions: In competitive experiments in ternary solutions of C2Cl4 and C2Cl3F in cyclohexane the rate constant ratio k2c/k2a was determined By comparing with previous data for the addition of cyclohexyl radicals to other chloroethylenes it is shown that in certain cases the trends in activation energies for cyclohexyl radical addition can be correlated with the C? Cl bond dissociation energies in the adduct radicals. 相似文献
The pyrolyses of endo- and exo-5-methylbicyclo (2.2.2) oct-2-ene (endo- and exo-MBO) have been studied between 608 and 679°K at pressures between 7 and 37 torr. These reactions correspond to parallel first-order eliminations of propene and ethylene: The rate constants (in sec?1) for endo-MBO are given by and those for exo-MBO by Reaction mechanisms involving diradicals are shown to be compatible with the experimental results. The heats of formation and the entropies of endo and exo-MBO are estimated. 相似文献
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
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
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
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
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
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
The thermal decomposition of ammonia was studied by means of the shock-tube and vacuum ultraviolet absorption spectroscopy monitoring the concentration of atomic hydrogen. The rate constants of both the initiation reaction and the consecutive reaction were determined directly as and respectively. 相似文献
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
A transformation exists which allows the general Riccati equation to be written in a simpler form: The transformed equation has the equivalent nonlinear Hammerstein integral equation if the kernel N(r, r′) satisfies three conditions: and and A solution of the nonlinear integral equation is devised by repeatedly integrating the Hammerstein equation. During this procedure the kernel generates an equation that contains only coefficients of β(r)0 and β(r)1. As a result, after truncating at the end of the nth cycle, it is a simple matter to write down a Padé-type approximation: all coefficients in this approximation are capable of being evaluated in terms of simple algebraic formulations of P(r), R(r), and integrals over P(r). The zeroes of the denominator of the Padé-type approximation define the points where singularities occur in β(r). 相似文献
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
On the basis of the thermal decomposition of mixtures of propylene and propane with molar ratios of 0.0–0.33 in the temperature range 779–812K, the influencing functions describing the inhibition by propylene of the decomposition of propane were determined. The rate-reducing effect is explained mainly by the reactions (in which .R = .H, .CH3 and 2-?3H7) and also by the addition reactions It was established that the bulk of the allyl radicals formed participate in the chain step, but, due to their lower reactivity, they restore the decomposition chain more slowly than the original radicals do. From the characteristic change in the ratio υ/υ, the rate ratios of hydrogenabstraction reaction by radicals from propylene and propane could be determined. In these reactions there was no significant difference between the selectivities of the radicals. For an interpretation of the changes, the decomposition mechanism must be completed with the reaction Evaluation of the influencing curves revealed that the initiation reactions must be taken into account. By parameter estimation we have determined the rate ratios characterizing the above initiation reactions, the unimolecular decomposition of propane, hydrogen abstraction by radicals from propane and propylene, intermolecular isomerization of the 2-propyl radical via propane and propylene, and abstraction of propane hydrogens by the ethyl and methyl radicals; these are given in Tables II. 相似文献
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
The kinetics of the gas-phase decomposition of bicyclo[4.1.0]heptane has been studied over the temperature range of 708–769 K at pressures between 1 and 17 torr. Isomerization to 1-methylcyclohex-1-ene, methylenecyclohexane, and cycloheptene accounts for 96–98% of the primary reaction products and occurs by first-order, homogeneous, nonradical processes. 相似文献
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
The kinetics of the gas-phase reaction of 2,2,2-trifluoroethyl iodide with hydrogen iodide has been studied over the temperature range of 525°K to 602°K and a tenfold variation in the ratio of CF3CH2I/HI. The experimental results are in good agreement with the expected free radical-mechanism: An analysis of the kinetic data yield: where θ =2.303RT in kcal/mol. If these results are combined with the assumption that E2 = 0 ± 1 kcal/mol, then one obtains DH (CF3CH2? I) = 56.3 kcal/mol. This result may be compared with DH(CH3CH2? I) = 52.9 kcal/mol and suggests that substitution of three fluorines for hydrogen in the beta position strengthens the C? I bond slightly. 相似文献