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 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
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
4-Methylhexyne-1, 5-methylhexyne-1, hexyne-1, and 6-methylheptyne-2 have been decomposed in comparative-rate single-pulse shock-tube experiments. Rate expressions for the initial decomposition reactions at 1100°K and from 2 to 6 atm pressure are In combination with previous results, rate expressions for propargyl C? C bond cleavage are related to that for the alkanes by the expression These results yield a propargyl resonance energy of D(nC3H7-H) – D(C3H3-H) = 36 ± 2 kJ, in excellent agreement with a previous shock-tube study. They also lead to D(CH3C≡CCH2-H) – D(C3H3-H) = 0.6 ± 3 kJ, D(sC4H9-H) – D(iC3H7-H) = 0 ± 3 kJ, D(iC4H9-H) – D(nC3H7-H) = 2 ± 3 kJ, and D(nC3H7-H) – D(iC3H7-H) = 13.9 ± 3 kJ (all values are for 300°K). The systematics of the molecular decomposition process are explored. 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
Acetylene and vinylacetylene mixtures were pyrolyzed at 400-500°C in the absence and presence of O2 or NO. The major product of the interaction between C2H2 and C4H4 is polymer, but benzene is also produced. Both the C2H2 removal and C6H6 formation rates arefirst-order in C2H2 and C4H4. The rate coefficients are where R is the ideal gas constant in kJ/mol-K. Benzene formation occurs by two processes: a concerted molecular mechanism (?60%) and a singlet diradical mechanism (?40%). 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
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 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 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
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
The reactions have been studied competitively in the vapor phase over the range of 52–204°C. The i-C3F7 radicals were generated by means of the reaction It was found that where θ = 2.303RT J/mol. Absolute Arrhenius parameters are derived for the reactions where R = CF3, C2F5, and i-C3F7. 相似文献
The title reaction has been investigated in the temperature range of 490-573 K. Initial reactant pressures were varied in the range of 0.2-5.2 torr (I2) and 2-20 torr (C6H5SiH3). The rate of iodine consumption, monitored spectrophotometrically, was found to obey both by initial rate and integrated equation fitting procedures. The effect of added initial HI conformed to this expression. The data are consistent with a conventional I-atom propagated chain reaction, and for the step the rate constant is given by From this is derived the bond dissociation energy value C6H5SiH2? H = 374 kJ/mol(88 kcal/mol). A comparison with other Si? H dissociation energy values indicates that the “silabenzyl” stabilization energy is small, ≈7 kJ/mol. 相似文献
The photolysis of cis-1,2-dichloroethylene has been investigated in the presence of I2 as a function of incident wavelength and as a function of initial cis pressure. The results indicate that at ± > 2200Å the following primary processes occur: The lifetime of the excited state yielding the above products is estimated at about 2.4×10?9 sec. At shorter wavelengths additional C2H2 is produced by decomposition of a vibrationally excited C2H2Cl radical. Scavenging of the CHClCH radical by I2 produced trans and cis-CHClCHl in a ratio of 4 to 1, respectively. 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 gas-phase decompositions of methylsilane and methylsilane-d3 have been investigated in a single-pulse shock tube at 4700 torr total pressure in the temperature range of 1125–1250 K. For CH3SiD3 at 1200 K three primary steps occur in the homogeneous decomposition with efficiencies in parentheses: , , and . For CH3SiH3 at 1200 K the primary CH4 elimination efficiency is 0.09 while the total primary H2 elimination efficiency is 0.91. Minor product formations of C2H4, acetylene, dimethylsilane, and SiH4 are discussed. 相似文献
2,4-Dimethylhexene-l has been decomposed in single-pulse shock tube experiments. Rate expressions for the initial reactions are and sec?1 at 1.5–5 atm and 1050°K. This leads to ΔH°f300 (CH2 = C(CH3)CH2) = 124 kJ/mol, or an allylic resonance energy of 50 kJ/mol. Rate expressions for the decomposition of the appropriate olefins which yield isobutenyl radicals and methyl, ethyl, isopropyl, n-propyl, t-butyl, and t-amyl radicals, respectively, are presented. The rate expression for the decomposition of isobutenyl radical is (at the beginning of the fall-off region). For the combination of isobutenyl and methyl radicals, the rate constant at 1020°K is Combination of this number and the calculated rate expression for 2-methylbutene-1 decomposition gives S. (1100) = 470 J/mol °K. This yields It is demonstrated that an upper limit for the rate of hydrogen abstraction by isobutenyl from toluene is 相似文献
2-Methylbut-1-ene-3-yne and Propyne mixtures were pyrolyzed at 350–450°C in the absence and presence of O2 and NO. The major product of the reaction is a polymer, but m-xylene and p-xylene are also produced and were studied as the species of interest. The C8H10 formation rate is first-order in C3H4 and C5H6. The rate coefficient is best fitted by though it is not inconsistent with where R is the ideal gas constant in kJ/mol-K. Experiments in the presence of NO show that m-xylene and p-xylene formation occur by two processes: a concerted molecular mechanism (? 41%) and a singlet diradical mechanism (? 59%). 相似文献
A mixture of Br2 + HBr + C2F5I was photolyzed in the vapor phase. The reaction forms C2F5 radicals which are removed by Competitive studies over the range of 74–146°C gave ratios of k10/k9, and these were combined with values obtained previously by different methods at higher temperatures upto 515°C to give where θ = 2.303RT J/mol. A value is assigned to the activation energy E10, and this, with other data, leads to at 25°C. This result is in excellent agreement with two previous independent determinations. 相似文献