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61.
Numerical results for the density and current correlation functions in dense hard-sphere fluids are obtained from a kinetic equation which is the extension of the linearized Enskog equation to finite wavelengths in order to demonstrate the convergence of the method of solution. Comparison is made to a previously proposed approximate solution.This work was performed in part under the auspices of the U.S. Department of Energy by the Lawrence Livermore Laboratory under contract number W-7405-ENG-48 and in part supported by the National Science Foundation. 相似文献
62.
The negative temperature dependence, pressure dependence, and isotope effects of the self-reaction of HO2 are modeled, using RRKM theory, by assuming that the reaction proceeds via a cyclic, hydrogen-bonded intermediate. The negative temperature dependence is due to a tight transition state, with a negative threshold energy relative to reactants, for decomposition of the intermediate to products. A symmetric structure for this transition state reproduces the observed isotope effect. The weak pressure dependence for DO2 self-reaction is due to the approach to the high-pressure limit. Addition of a polar collision partner, such as ammonia or water vapor, enhances the rate by forming an adduct that reacts to produce deexcited intermediate. A detailed model is presented to fit the data for these effects. Large ammonia concentrations should make it possible to reach the high-pressure limit of the self-reaction of HO2. 相似文献
63.
An analysis of the thermochemistry of the kinetic parameters of the elementary reactions involved in the pyrolysis of pentachloroethane has resolved several disputed, unclarified, or inconsistent aspects of the reaction mechanism. The resulting mechanisms for the inhibited and uninhibited pyrolysis account for all reported experimental findings. On the basis of this interpretation, first experimentally based values have been derived for the following: DH0(CCl3–CHCl2) = 79.0 ± 1.0 kcal/mol, ΔH(CHCl2) = 25.7 ± 1.0 kcal/mol, and E1 = 59.7 ± 1.0 kcal/mol C2HCl5 . 相似文献
64.
Equilibrium constants for the reaction CH3COCH2CH3 + I2 ? CH3COCHICH3 + HI have been computed to fit the kinetics of the reaction of iodine atoms with methyl ethyl ketone. From a calculated value of S(CH3COCHICH3) = 93.9 ± 1.0 gibbs/mole and the experimental equilibrium constants, ΔH(CH3COCHICH3) is found to be ?38.2 ± 0.6 kcal/mole. The Δ(ΔH) value on substitution of a hydrogen atom by an iodine atom in the title compound is compared with that for isopropyl iodide. The relative instability of 2-iodo-3-butanone (3.4 kcal/mole) is presented as further evidence for intramolecular coulombic interaction between partial charges in polar molecules. The unimolecular decomposition of 2-iodo-3-butanone to methyl vinyl ketone and hydrogen iodide was also measured in the same system. This reaction is relatively slow compared to the formation of the above equilibrium. Rate constants for the reaction over the temperature range 281°–355°C fit the Arrhenius equation: where θ = 2.303RT kcal/mole. The stability of both the ground and transition states is discussed in comparing this activation energy with that reported for the unimolecular elimination of hydrogen iodide from other secondary iodides. The kinetics of the reaction of hydrogen iodide with methyl vinyl ketone were also measured. The addition of HI to the double bond is not rate controlling, but it may be shown that the rate of formation of 1-iodo-3-butanone is more rapid than that for 2-iodo-3-butanone. Both four- and six-center transition complexes and iodine atom-catalyzed addition are discussed in analyzing the relative rates. 相似文献
65.
C. M. Stevens Louis Kaplan Robert Gorse Susan Durkee Michael Compton Sidney Cohen Karen Bielling 《国际化学动力学杂志》1980,12(12):935-948
The kinetic isotope effect (KIE) for carbon and oxygen in the reaction CO + OH has been measured over a range of pressures of air and at 0.2 and 1.0 atm of oxygen, argon, and helium. The reaction was carried out with 21–86% conversion under static conditions, utilizing the photolysis of H2O2 as a source of OH radicals. The value of the KIE for carbon varies with pressure and the kind of ambient gas; for air the ratio of the reaction rates 12k/13k has the value 1.007 at 1.00 atm and decreases to 0.997 at 0.2 atm; for oxygen and argon over the same pressure range the values are 1.002–0.994 and 1.000–0.991, respectively. The value of the KIE for the CO oxygen atom is 16k/18k = 0.990 over the pressure range 0.2–1.0 atm and is independent of the kind of ambient gas. No exchange of the oxygen atoms in the activated complex, followed by decomposition to the starting molecules, was observed. From the mechanistic standpoint the normal KIE observed for carbon at the high pressure is attributed to the initial formation of the activated HOCO radical, whereas the inverse KIE observed at low pressures is a result of the KIE for the reverse reaction HOCO? → CO + OH being greater than that for the forward reaction HOCO? → CO2 + H. The derived isotopic equilibrium constant for HOCO ?CO favors the enrichment of 13C in the more strongly bound HOCO. 相似文献
66.
We derive 't Hooft's consistency condition on the bound-state spectrum of a confining field theory from the principles of analytic S-matrix theory. 相似文献
67.
The decomposition rate constant of i-PrI under conditions of very low-pressure pyrolysis (VLPP) is completely consistent with the well-known high-pressure Arrhenius parameters and the RRK(M) theory. The decomposition of n-PrI under the same conditions proceeds via two pathways, the anti-Markownikoff dehydroiodination and C? I bond scission. The data, analyzed by taking into account the mutual interaction of the two pathways, is completely consistent with the known Arrhenius parameters for the bond scission step and, when combined with a reasonable A-factor, yields an activation energy for HI elimination which is as predicted for these semi-ion pair transition states. 相似文献
68.
Sidney Toby 《Journal of luminescence》1973,8(1):94-96
The reaction between ozone and allene is accompanied by chemiluminescence extending from 325–525 nm. The well-resolved spectrum obtained is that of electronically excited formaldehyde (1A2). Unlike the case for mono-olefins studied by Finlayson and Pitts [1] no other emission was seen. 相似文献
69.
The very low pressure reactor (VLPR) technique has been used to measure the bimolecular rate constant of the title reaction at 300 K. The rate constant is given by log k1 (1/mol s) = (11.6 ± 0.4) ? (5.9 ± 0.6)/θ the equilibrium constant has also been measured at the same temperature and is given by K1 = (5.6 ± 1) × 10?3 and hence log k?1 (1/mol s) = 9.5 ± 0.1. The results show that the reaction Br + t? C4H9 → HBr + i? C4H8 is unimportant under the present experimental conditions. Assigning the entropy of t-butyl radical to be 74 ± 2 eu which is in the possible range, the value of K1 gives ΔH (t-butyl) = 9.1 ± 0.6 kcal/mol?1. This yields for the bond dissociation, DH° (t-butyl-H) = 93.4 ± 0.6 kcal/mol. Both of these values are found to be in good agreement with recent VLPP studies. 相似文献
70.
We prove that the ultimate fate of a bubble of negative energy density which forms in a metastable universe of zero energy density is gravitational collapse. We improve on previous treatments in that we allow for departures from O(3, 1) symmetry in the initial state, so long as they are not too great. 相似文献