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21.
By investigation of isomeric 2H- and 13C-labelled C9H11 Cl-compounds it has been shown that the ion [M ? Cl]+ is transformed mainly to the ion [C7H7]+ via C2H4-elimination from alkyl-substituted tropylium-ions. Phenyl-cyclopropane-cations play only a small part, if at all, in this fragmentation process. 相似文献
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Cornelia Bohne Adelaide Faljoni-Alario Giuseppe Cilento 《Photochemistry and photobiology》1988,48(3):341-347
Abstract— The interaction of serum albumin-bound acceptors with enzyme-generated and protected triplet species was studied in two types of systems. Chlorophyll-a bound to bovine and human serum albumins is efficiently excited by enzymatically generated triplet acetone and acetaldehyde. When the Chl-a concentration is much lower than that of the albumin the interaction occurs with chlorophyll in an aggregate in which one Chl-a is surrounded by several protein molecules. When the Chl-a concentration is higher than that of the protein, the aggregate contains the proteins and fluorescent chlorophylls in a 1:1 ratio. The excess chlorophylls, although able to interact with the donors, are not fluorescent.
In another study, probes bound to various specific sites of serum albumins were used as quenchers of the enzymatically generated triplet acetone. The efficiency of quenching by all the bound probes is equal and in one case even stronger than for the free probes.
A model for the interaction of the excited species contained in the enzyme with the acceptor(s) located in the protein is proposed.
The present results provide further evidence that enzyme-generated and protected triplet carbonyl species can interact through a collisional process with acceptors bound to or constituents of macromolecules. 相似文献
In another study, probes bound to various specific sites of serum albumins were used as quenchers of the enzymatically generated triplet acetone. The efficiency of quenching by all the bound probes is equal and in one case even stronger than for the free probes.
A model for the interaction of the excited species contained in the enzyme with the acceptor(s) located in the protein is proposed.
The present results provide further evidence that enzyme-generated and protected triplet carbonyl species can interact through a collisional process with acceptors bound to or constituents of macromolecules. 相似文献
26.
"Bare" CeO(2)(+) ions can be prepared in the gas phase by consecutive oxidation of Ce(+) with O(2) and NO(2). The ability to activate saturated and unsaturated hydrocarbons is investigated by use of Fourier-transform ion cyclotron resonance mass spectrometry. In the reactions of CeO(2)(+) with linear and branched alkanes C-H bond activation is observed almost exclusively. In contrast, both oxygen-atom transfer and C-H bond activation processes occur when thermalized CeO(2)(+) cations react with simple alkenes and aromatic compounds. C-C bond activation is not observed at all. Insight into the structural and electronic properties of neutral CeO(2) and cationic CeO(2)(+) is provided by means of quasirelativistic density-functional and ab initio pseudopotential calculations. They reveal a (2)Sigma(u)(+) ground state for CeO(2)(+) which is best described as a linear cerium dioxide with a resonating pi bond. Finally, we discuss the influence of oxo ligands on the chemistry of the cationic CeO(n)()(+) (n = 0-2) species toward hydrocarbons. 相似文献
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S. G. Wang Y.X. Qiu E. Neumann H. J. Deiseroth W. H. Eugen Schwarz 《无机化学与普通化学杂志》2003,629(10):1718-1730
About 60 molecular species composed of up to 10 mercury atoms and of oxygen atoms and/or of some other elements or groups (such as halogen, OH2, OH, H, alkali, NO3) have been investigated quantum chemically. Different density functional approaches and the ab initio SCF‐MP2 method were applied, comparing different basis sets and different atomic core sizes. It is important not to treat the Hg 5s, p, d as inactive core shells, and to use sufficiently many polarization functions. The shape of the 〉O‐Hg‐Hg‐O〈 units is not favorable concerning the formation of lattices composed of HgI, O and OH only. Despite its bulkiness, the OHgHgO units can easily come into contact with each other and then disproportionate. This is prevented in the so‐called ternary M‐HgI oxides by the embedded oxometallate (oxoacidic) anions. Furthermore, the HgI and HgII oxide bond energies are less favorable towards the stability of HgI oxo compounds, as compared to Hg halidic or oxoacidic compounds. Both points are not promising concerning the search for HgI oxides/hydroxides, although the preparation of such compounds, including spacer groups, by topochemical reactions can still not be excluded. So far, experimental efforts towards the synthesis of such a new class of compounds have only demonstrated that HgII is strictly preferred over HgI in the formation of solids of binary Hg‐O or ternary A‐Hg‐O composition (A = electropositive metal such as alkali, in contrast to M = transition or semi‐metal). This is so even if compounds containing ‘electron rich Hgδ— atoms’ (i.e. A‐Hg amalgams) are oxidized under mild conditions. 相似文献
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The products of decomposition of solutions of p-chlorobenzenediazonium tetrafluoroborate in aqueous buffer solutions (pH 9.0–10.3; ionic strength 0.1–0.5) at 20.0° have been analyzed quantitatively. Up to eleven low molecular weight compounds could be identified besides the major product, the complex polymeric diazo tar. The distribution of products is influenced by trace amounts of oxygen as well as by p-chlorophenol and the radical trapping reagent iodoacetic acid. Mechanisms of formation of the products are discussed. 相似文献
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Pd/P(t-Bu)(3) serves as an unusually reactive catalyst for Stille reactions of aryl chlorides and bromides, providing solutions to a number of long-standing challenges. An unprecedented array of aryl chlorides can be cross-coupled with a range of organotin reagents, including SnBu(4). Very hindered biaryls (e.g., tetra-ortho-substituted) can be synthesized, and aryl chlorides can be coupled in the presence of aryl triflates. The method is user-friendly, since a commercially available complex, Pd(P(t-Bu)(3))(2), is effective. Pd/P(t-Bu)(3) also functions as an active catalyst for Stille reactions of aryl bromides, furnishing the first general method for room-temperature cross-couplings. 相似文献