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941.
942.
The ring-retaining products formed from the OH radical-initiated reactions of o-, m-, and p-xylene in the presence of NOx have been identified and their formation yields determined. Experiments were carried out at 298 ± 2 K and in the presence of 740 torr total pressure of air. The products observed, and their yields, were: from o-xylene, o-tolualdehyde, 0.0453; 2-methylbenzyl nitrate, (0.0135 + 5.5 × 10?17 [NO2]); 2,3-dimethylphenol, 0.097; 3,4-dimethyl-phenol, 0.064; 3-nitro-o-xylene, 0.0059; 4-nitro-o-xylene, (0.0111 + 9.9 × 10?17 [NO2]); from m-xylene, m-tolualdehyde, 0.0331; 3-methylbenzyl nitrate, 0.0061; 2,4-dimethylphenol, 0.099; 2,6-dimethylphenol, 0.111; 4-nitro-m-xylene, 0.0018; 5-nitro-m-xylene, (0.0032 + 1.6 × 10?17 [NO2]); from p-xylene, p-tolualdehyde, 0.0701; 4-methylbenzyl nitrate, 0.0082; 2,5-dimethylphenol, 0.188, 2-nitro-p-xylene, (0.0120 + 2.8 × 10?17 [NO2]), where the NO2 concentration is in molecule cm?3 units. The nitro-xylene data are consistent with our recent product study of the corresponding reactions of benzene and toluene and indicate that under the experimental conditions employed the dimethylhydroxycyclohexadienyl radicals reacted with NO2 and not with O2. When combined with literature ring-cleavage product yields, these data show that ca. 55–80% of the reaction pathways are accounted for. 相似文献
943.
Without invoking macrorealism, we derive a contradiction between the quantum mechanical predictions forsquid's and two intuitive conditions. First, we assume that asquid can be measured without significantly disturbing its subsequent macroscopic behavior. Second, we assume a trivial realism condition much weaker than Leggett's macrorealism. Quantum mechanics itself obeys our realism assumption. This proof suggests that althoughsquid experiments cannot rule out macrorealism, they can rule out most theories that allow noninvasive measurements. 相似文献
944.
Roger Atkinson Sara M. Aschmann Ernesto C. Tuazon Janet Arey Barbara Zielinska 《国际化学动力学杂志》1989,21(7):593-604
3-Methylfuran has been identified as a product of the gas-phase reaction of the OH radical with isoprene, and under simulated atmospheric conditions a formation yield of 0.044 ± 0.006 was determined. In an analogous manner, the OH radical reaction with 1,3-butadiene formed furan with a yield of 0.039 ± 0.011. Using a relative rate method, a rate constant for the reaction of the OH radical with 3-methylfuran of 9.35 × 10?11 cm3 molecule?1 s?1 (with an estimated overall uncertainty of ±20%) at 296 ± 2 K was also determined. These data show that 3-methylfuran is a reactive compound which will be present in the troposphere at concentrations ?5% of those of its isoprene precursor. 相似文献
945.
A quantum system whose state vector belongs to a finite-dimensional Hilbert space is considered. If this space has a dimension that is a composite number, one can factor the space into a tensor product of sub-spaces. An observable that acts only in one of these subspaces is called a partial measurement. Some of the properties and the interpretation of such partial measurements are discussed. 相似文献
946.
Metin Balci Susan A. Bourne Abdullah Menzek Nurullah Saraçoglu William H. Watson 《Journal of chemical crystallography》1995,25(3):107-116
Syn- andanti-isomers of substituted tetracyclo[6.2.2.23.6.12.7]tetradeca-2(7)-ene have been synthesized. In thesyn-isomers steric interactions between cyclopropane hydrogen atoms lead to a pyramidalization of the C(sp2) atoms of the central double bond. The parameters from three crystal structures are compared with geometry optimized structures using PCWIN, MM3, and MOPAC. Plots of X-ray distances versus theoretically optimized distances give correlation coefficients between 0.91 and 0.97. Analysis of the discrepancies suggest modifications in some molecular mechanics parameters are needed to model the solid state structures. 相似文献
947.
Rate constants for the gas-phase reactions of NO3 radicals with a series of alkynes, haloalkenes, and α,β-unsaturated aldehydes have been determined at 298 ± 2 K using a relative rate technique. Using rate constants for the reactions of NO3 radicals with ethene and propene of (1.1 ± 0.5) × 10?16 cm3 molecule?1 s?1 and (7.5 ± 1.6) × 10?15 cm3 molecule?1 s?1, respectively, the following rate constants (in units of 10?16 cm3 molecule?1 s?1) were obtained: acetylene, ≤0.23; propyne, 0.94 ± 0.44; vinyl chloride, 2.3 ± 1.1; 1,1-dichloroethene, 6.6 ± 3.1; cis-1,2-dichloroethene, 0.75 ± 0.35; trans-1,2-dichloroethene, 0.57 ± 0.27; trichloroethene, 1.5 ± 0.7; tetrachloroethene, <0.4; allyl chloride, 2.9 ± 1.3; acrolein, 5.9 ± 2.8; and crotonaldehyde, 41 ± 9. The atmospheric implications of these data are discussed. 相似文献
948.
Using a relative rate method, rate constants for the gas-phase reactions of the OH radical with trans-pinane [(1R, 2R)-2, 6, 6-trimethylbicyclo[3.1.1]heptane], tricyclene (1, 7, 7-trimethyltricyclo[2.2.1.02, 6]heptane), and quadricyclane (quadricyclo[2.2.1.02, 6.03, 5]heptane) of (1.34 ± 0.29) × 10?11 cm3 molecule?1 s?1, (2.86 ± 0.62) × 10?12 cm3 molecule?1 s?1 and (1.83 ± 0.41) × 10?12 cm3 molecule?1 s?1, respectively, have been determined at 296 ± 2 K. These rate constants are compared with values calculated from an empirical estimation method and used to refine this estimation technique for the calculation of OH radical reaction rate constants for polycyclic systems. © John Wiley & Sons, Inc. 相似文献
949.
Using a relative rate method, rate constants have been determined at 296 ± 2 K for the gas-phase reactions of the OH radical with toluene, the xylenes, and the trimethylbenzenes. Using the recommended literature rate constant for the reaction of OH radicals with propene of (2.66 ± 0.40) × 10?11 cm3 molecule?1 s?1, the following rate constants (in units of 10?12 cm3 molecule?1 s?1) were obtained: toluene, 5.48 ± 0.84; o-xylene, 12.2 ± 1.9; m-xylene, 23.0 ± 3.5; p-xylene, 13.0 ± 2.0; 1,2,3-trimethylbenzene, 32.7 ± 5.3; 1,2,4-trimethylbenzene, 32.5 ± 5.0; and 1,3,5-trimethylbenzene, 57.5 ± 9.2. These data are compared with the literature values. 相似文献
950.
Rate constants for the gas-phase reactions of NO3 radicals with a series of cycloalkenes have been determined at 298 ± 2 K, using a relative rate technique. Using an equilibrium constant for the NO2 + NO3 ? N2O5 reactions of 3.4 × 10?11 cm3 molecule?1, the following rate constants (in units of 10?13 cm3 molecule?1 s?1) were obtained: cyclopentene, 4.52 ± 0.52; cycloheptene, 4.71 ± 0.56; bicyclo[2.2.1]-2-heptene, 2.41 ± 0.28; bicyclo[2.2.2]-2-octene, 1.41 ± 0.17; bicyclo[2.2.1]-2,5-heptadiene, 9.92 ± 1.13; and 1,3,5-cycloheptatriene, 12.6 ± 2.9. When combined with previous literature rate constants for cyclohexene and 1,4-cyclohexadiene, these data show that the rate constants for the nonconjugated cycloalkenes studied depend to a first approximation on the number of double bonds and the degree and configuration of substitution per double bond. No obvious effects of ring strain energy on these NO3 radical addition rate constants were observed. Our previous a priori predictive techniques for the alkenes and cycloalkenes can now be extended to strained cycloalkenes. 相似文献