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11.
The reaction of B2H4 with acetylene has been studied by the MNDO method. It is shown that the reaction is exothermic and proceeds in two steps. The first step is the formation of a three-center -complex and this is the rate-determining step of the reaction. The second step is the rearrangement of the -complex to the product and this step requires a very small amount of activation energy. The activation barrier for the diboration reaction is 12.8 kcal/mol.The proposed mechanism is significantly different from those proposed earlier and explains all experimental data relating to this reaction. 相似文献
12.
Ray K Nakahara H Sakamoto A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(1-2):103-107
The fluorescence lifetimes decays and picosecond time-resolved fluorescence spectra were measured to investigate the dynamics of the excited state of sulforhodamine B (SRB) molecules adsorbed in the mono- and multilayered Langmuir-Blodgett (LB) films of octadecylamine. Steady-state and time-resolved fluorescence spectroscopy reveals that the fluorescence lifetimes and contents of the monomer and dimers in the molecular organizates depend upon the concentration of the dye in the solution and the adsorption process. SRB dye molecules adsorbed in LB films have been imaged with scanning near-field optical microscopy (SNOM). This information is exploited to map the distribution with molecular spatial resolution. SNOM provide the visual evidence of the monomers and dimers of SRB in cationic LB films. 相似文献
13.
Deuterium labeling in the acetate derivatives of cholic acid demonstrates that electron impact induced consecutive loss of HOAc from the molecular ion occurs in the following order of decreasing preference: 12α-OAc > 7α-OAc > 3α-OAc. Numerous examples are presented showing that consecutive loss of HOAc from a common ion generally increases progressively with relative intensity. In the acetate pregnan-20-one derivatives of cholic acid, loss of 43 mass units from the molecular ion comes from the 12α-OAc and not the 17β-acetyl sidechain. Ketene is ejected from an acetoxy group located in an α position to a carbonyl on which an ion-radical charge is localized. 相似文献
14.
Jerry Ray Dias 《Journal of mathematical chemistry》1990,4(1):17-29
The genesis of the aufbau and excised internal structure concepts is traced. These concepts were pivotal to the first published enumerations of the strictly peri-condensed, non-Kekuléan, and essentially strain-free total resonant sextet benzenoid groups. Aperiodic table set is defined as a partially ordered set forming a two-dimensional array which complies with thetriad principle where a central element has a metric property that is the arithmetic mean of two adjacent surrounding member elements. 相似文献
15.
Paital AR Mitra T Ray D Wong WT Ribas-Ariño J Novoa JJ Ribas J Aromí G 《Chemical communications (Cambridge, England)》2005,(41):5172-5174
Based on a combined theoretical-experimental study, we propose that substituted m-phenylene ligands (m-N-Phi-N) can act as tuneable strong ferromagnetic couplers connecting Cu(II) ions; a new complex presenting that bridge with J close to +15 cm(-1) has been suggested and synthesized. 相似文献
16.
Jerry Ray Dias 《Journal of mathematical chemistry》1990,4(1):127-142
The molecular orbital parameters for tricarbonyl(tetrahapto-unsaturated-hydrocarbon)iron complexes are computed using graph-theoretical methods. The results are in agreement with their experimental properties. 相似文献
17.
Liu B. Thomas P. S. Ray A. S. Williams R. P. 《Journal of Thermal Analysis and Calorimetry》2004,76(1):115-122
The effect of sampling conditions on the decomposition of electrolytic manganese dioxide using thermal methods is reported.
Significant differences were observed in the mechanism of the decomposition by simply changing the reaction environment from
a closed pan to an open pan configuration. The purge gas atmosphere was also observed to influence the decomposition mechanism.
As a product of the decomposition is oxygen, the change in the mechanism observed between the experimental conditions may
be explained in terms of the ease of removal of oxygen from the reaction site.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
A thermal analysis study on the reduction of iron oxide rich slags under different conditions is presented in this paper. The effects of important process variables such as time, temperature, lime-silica ratio, FeO level in slag etc. are discussed. It is shown that the mechanism of reduction by externally added graphite is different from that by a carbon saturated bath although the activation energy values are similar. 相似文献
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