Compounds, continued molecular

Chiral compounds (Continued) epoxy alcohols, 141 formulas, xiii xvii hydroxystannanes, 318 liquid crystals, 350 molecular lattics, 347 natural, 1 NMR spectra, 282 olefins, 173 oxetanones, 326 phenols, 287 see also Binaphthol phenylbutenes, 172 protonating agents, 324 sulfoxides, 159 sulfur ylides, 328 synthesis, I... 

Mixed-valence compounds continue to attract attention, not least because of their occurrence as intermediates of multistep redox systems Mixed-valence species are found in the geo- and biosphere, as evident from minerals such as Fe304 and from metalloproteins, where the Fe /Fe °/Fe, Cu /Cu and Mn / Mn Nn combinations are established Man-made mixed-valence compounds, starting from Prussian Blue in the early 18th century, have raised interest in what is now known as materials science because of their often special optical, electrical and magnetic properties These physical properties then prompted attempts at increasingly sophisticated levels to theoretically understand and computationally reproduce the experimental features of mixed-valence compounds More recent developments involve the application of mixed-valence systems as models and actual components in the areas of molecular electronics and molecular computing ... 

A new application of the g.l.c. quantitative analysis method for tetramethylsilyl ethers of alkaloids has been reported. Mass spectrometric investigations of galanthamine and related compounds continue to interest Russian workers. The important technique of chemical ionization (C.I.) mass spectrometry has been applied to the Amaryllidaceae as well as many other alkaloid types. This method offers several advantages over the conventional electron impact (E.I.) mass spectrometric determination a quasi-molecular ion QM ) formed by protonation or hydride abstraction in ion-molecule collisions is always present aliphatic hydroxy- and methoxy-functions can always be determined and skeletal rearrangement is always absent. 

By fast atomic bombardment (FAB) [11], ions of polar compounds with molecular mass up to 10000 Da may be generated.The sample is dissolved in a non volatile matrix (e.g., nitrobenzoic acid) and ionized by bombardment with neutral gas atoms, e.g., argon. Continuous-flow FAB (CF-FAB) [12] allows the use of the FAB-ionization technique in conjunction with an LC-coupling. 

The anomalous photophysical properties of sulphur compounds continue to attract interest. Quenching studies of the luminescent S2 state of a number of aromatic thioketones show a range of lifetimes between 10 and 10 s. A variety of solvents shows the role of transient interactive effects and environmental viscosity. In the case of the S2 state of thiophosgene in perfluoro-solvents, molecular dissociation is found to be the most... 

A detailed study of Cr(lll) speciation in human blood plasma was performed on continuous peritoneal dialysis patients (494). Total amounts and molecular mass distribution (by gel filtration) of Cr containing species in plasma samples were measured for 2 days after the addition of a single dose of CrCl3 into the dialysis solution. In the first 1-6 h, Cr(lll) was mainly bound to transferrin ( 80% in agreement with earlier results of animal studies) [(508) and references cited therein], and to a lesser extent to albumin. At later times, a shift of Cr(lll) to an unidentified compound with molecular mass of 5 kDa (possibly a small peptide) was observed. Binding of metal ions to small peptides... 

Allyl Compounds.—Mechanisms of intra- and inter-molecular rearrangement of 77-allyl compounds continue to attract much attention, with a variety of structural modifications being explored in attempts to render the interpretation of variable-temperature n.m.r. studies as unambiguous as possible. The possible modes of rearrangement have been conveniently summarised and discussed with particular reference to allyl compounds of rhodium, iridium, palladium, and platinum. This latter review emphasises the chemical aspects rather than the spectroscopic methods and the derivation of the kinetic results. 

In FAB methods, extensively used for compounds with molecular weight M <5000 g mol (e.g., polyglycols) [39, 40], the sample is dissolved in a matrix, which is a usually a viscous Uquid with low volatihty (e.g., glycerol). By bombarding the Uquid matrix with fast beams of atom, ions characteristic to the matrix and analyte are produced. The Uquid matrix provides continuous surface renewal and thus aUows primary beams to be used to produce intense and long-lasting spectra. One limitation of the method is the requirement for polymers to be miscible with the polar Uquid matrix. 

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