The kinetics of the liquid-phase hydrogenation of cyclodienes with various structures (endo-tricyclo[ 5.2.1.02,6]decadiene-3,8 and cis,cis-1,5-cyclooctadiene) by hydrogen over a finely dispersed 1%Pd/C catalyst at atmospheric pressure has been studied. The catalyst provides the possibility for successive saturation of the double bonds of the dienes. The reactivities of the cyclodienes determined by their electron-donating properties have been compared. The solvent nature is the determining factor in the ratio of hydrogen absorption rates in the case of successive saturation of the double bonds of the hydrocarbons. The hydrogenation kinetics of cyclic dienes, including dicyclopentadiene, can be modeled using the Langmuir–Hinshelwood equation when the process is carried out in a perfectly mixed flow reactor. 相似文献
We demonstrate the feasibility of fabrication of semiconducting nanowires (quantum dots) using F-actin as a template. Three
different approaches of assembling quantum dots into nanowires are described. The nanowires were characterized by fluorescence
microscopy. 相似文献
Traditional electron-transfer dissociation (ETD) experiments operate through a complex combination of hydrogen abundant and hydrogen deficient fragmentation pathways, yielding c and z ions, side-chain losses, and disulfide bond scission. Herein, a novel dissociation pathway is reported, yielding homolytic cleavage of carbon–iodine bonds via electronic excitation. This observation is very similar to photodissociation experiments where homolytic cleavage of carbon–iodine bonds has been utilized previously, but ETD activation can be performed without addition of a laser to the mass spectrometer. Both loss of iodine and loss of hydrogen iodide are observed, with the abundance of the latter product being greatly enhanced for some peptides after additional collisional activation. These observations suggest a novel ETD fragmentation pathway involving temporary storage of the electron in a charge-reduced arginine side chain. Subsequent collisional activation of the peptide radical produced by loss of HI yields spectra dominated by radical-directed dissociation, which can be usefully employed for identification of peptide isomers, including epimers.
A new acid-base fluorescent switch containing both imidazo[4,5-f][1,10]-phenanthroline and triphenylamine groups has been synthesized.Its fluorescence emissions and absorptions can be reversibiy changed through protonation/deprotonation of imidazole and amine moiety by controlling the intramolecular charge transfer(ICT) process,leading to off-on-off fluorescent molecular switching. 相似文献
A sulfate-encapsulating complex, [Cu(1)L(6)]·3[Cu(2)L(2)(DMF)(4)](SO(4))(4) (1, L = N-(1-naphthyl)-N'-(3-pyridyl)urea) is synthesized in which two C(3)-clefts of the octahedral complexes interdigitate to form a cavity to encapsulate the sulfate ion by six urea groups. 相似文献
According to ab initio MO calculations at the G2(MP2) level of theory, branched isomers of dialkyl triselenides, R-Se(=Se)-Se-R (1; R = Me, Et), are less stable by more than 60 kJ mol(-1) than the isomeric unbranched chains R-Se-Se-Se-R (2). Therefore, species 1 cannot be generated in substantial concentrations under equilibrium conditions at moderate temperatures, as has recently been claimed by Meja and Caruso (Inorg. Chem. 2004, 43, 7486). Alternatively, the isomeric CH3-Se-CH2-Se-Se-Et (3) can be considered to explain the reported gas chromatograms and mass spectra previously assigned to Et-Se(=Se)-Se-Et (1b). However, the isomerization 2b --> 3 is also endothermic, by deltaG(o)298 = 63 kJ mol(-1). The isomeric selenols HSe-C2H4-Se-Se-Et (4) and CH3-CH(SeH)-Se-Se-Et (5) are also less stable than 2b (by ca. 56 kJ mol(-1)), but 4 is another candidate to explain the mass spectrum formerly assigned to 1b. The calculated structures of 1-5 are reported. 相似文献
Structural, protecting group and leaving group effects in the formation of oxocarbenium intermediates were studied in the gas phase. It is found that significant stabilization of oxocarbenium cations is achieved by protecting groups that interact with the cationic center via neighboring group participation despite the electron-withdrawing character of these moieties. On the other hand, ethereal protecting groups do not facilitate the formation of oxocarbenium intermediates. The experimental findings are supported by DFT calculations that show the following order of stabilization by the group adjacent to the cationic center: RCO > SiR(3) > R, where R is an alkyl group. This indicates that the SN1-like mechanism that is commonly proposed for this reaction is not always valid. Moderate leaving group effect is also detected in a series of thioaryl glucopyranosides. 相似文献