Silicon-29 nuclear magnetic resonance

The molecular structure of polycarhosilane is difficult to represent precisely. However, from measurements of the molecular weight, the intrinsic viscosity, infared and ultraviolet spectroscopy, proton, carbon, and silicon nuclear magnetic resonance (IH, and 29SiNMR), and chemical analysis, the structure of polycarhosilane is found to be represented by three simple units. These are silicon bonded with four carbon atoms (SiC4), silicon bonded with three carbon atoms (SiCsH), and silicon bonded with x carbon atoms and 4 - x silicon atoms (SiCjcSi4-x, x = 1, 2, or 3). These are shown by the following stmctural units [18] ... 

The section on Spectroscopy has been retained but with some revisions and expansion. The section includes ultraviolet-visible spectroscopy, fluorescence, infrared and Raman spectroscopy, and X-ray spectrometry. Detection limits are listed for the elements when using flame emission, flame atomic absorption, electrothermal atomic absorption, argon induction coupled plasma, and flame atomic fluorescence. Nuclear magnetic resonance embraces tables for the nuclear properties of the elements, proton chemical shifts and coupling constants, and similar material for carbon-13, boron-11, nitrogen-15, fluorine-19, silicon-19, and phosphoms-31. 

Knight CTG, SD Kimade (1999) Silicon-29 nuclear magnetic resonance spectroscopy detection limits. A a/ Chem 71 265-267. 

Various methods have been applied to the analysis of silicones in general, and these have been well summarised elsewhere [22]. In particular, size exclusion chromatography (SEC) [23], nuclear magnetic resonance... 

Sindorf, D.W. and Maciel, G.E., Silicon-29 nuclear magnetic resonance study of hydroxyl sites on dehydrated silica gel surfaces, using silylation as a probe, J. Phys. Chem.,%1, 5516, 1983. 

Hoh, K.P., Ishida, H. and Koenig, J.L. (1990). Silicon-29 solid state nuclear magnetic resonance spectroscopy of composite interfaces. Polym. Composites 11, 121 125. 

In earlier literature reports, x-ray data of a-based ceramics, the /3-like phase observed in certain silica minerals was explained by a structural model based on disordered Q -tridymite. However, others have suggested that the structure of the stabilized jS-cristobalite-like ceramics is closer to that of a-cristobalite than that of Q -tridymite, based on the 29Si nuclear magnetic resonance (NMR) chemical shifts (Perrota et al 1989). Therefore, in the absence of ED data it is impossible to determine the microstructure of the stabilized jS-cristobalite-like phase. ED and HRTEM have provided details of the ceramic microstructure and NMR has provided information about the environments of silicon atoms in the structure. Infrared spectroscopy views the structure on a molecular level. 

Nuclear Magnetic Resonance Studies on Pentacoordinate Silicon Derivatives Relative Apicophilicity of X Groups at Silicon... 

Nuclear Magnetic Resonance (NMR). This technique is essentially based on the same principle as ESR, but NMR is capable of detecting nuclei (MHz) instead of electrons (GHz). (Lack of a standardized nomenclature has resulted in numerous modifiers in connection with magnetic resonance instrumentation—electron, proton, nuclear, etc, plus apphcaaon-related terms, such as silicon-29, oxygen-17, nC S,P NMR, elc.)... 

Silicagel is also called silica or bare silica. Its adsorptive properties depend on the hydroxyl groups attached to surface silicon atoms. Silicagel has a maximum silanol density of 8.0 yumolcs/ m2. Many of these silanols are buried deep in the porous structure and are available only to the smallest analytes. Silanols are either isolated, geminal, or vicinal they can be distinguished by means of Si solid-state nuclear magnetic resonance (NMR). The surface also contains siloxane bonds (Si-O-Si), which are considered hydrophobic. 

Nuclear Magnetic Resonance Spectra of Oiganometallic Compounds, 3, I Nucleophilic Displacement at Silicon Recent Developments and Mechanistic Implications, 20, 265... 

Various methods may be used to examine configurations of polysilanes, but 29Si NMR spectroscopy has been the most useful. Silicon-29, like carbon-13, has spin 1/2 and a relatively low abundance, 4.7%. Nuclear magnetic resonance (NMR) spectroscopy using 29Si has been important for the characterization of siloxane polymers, and is proving to be equally useful for polysilanes. 

The organopolysilanes are those compounds containing at least one silicon-silicon bond and one silicon-carbon linkage. This review is mainly concerned with the chemistry of aliphatic derivatives of polysilanes. Consideration of aromatic organopolysilanes is excluded from this review except as far as they are used as intermediates for synthesis and their properties correlate with the aliphatic silicon-silicon compounds, because the aromatic organopolysilanes have recently been well reviewed elsewhere (31,51, 73, 76a, 212). Physical properties of the polysilanes also are excluded from consideration except for spectral properties of ultraviolet absorption and nuclear magnetic resonance, since they are well summarized in earlier excellent reviews and texts (8, 34, 35, 51,131,132). 

Sjoberg, S. and Ohman, L.-O. (1985) Equilibrium and structural studies of silicon (IV) and aluminium (III) in aqueous solution. Part 13. A potentiometric and 27A1 nuclear magnetic resonance study of speciation and equilibria in the aluminium(III)-oxalic acid-hydroxide system.f. Chem. Soc. Dalton Trans., 12, 2665-2669. 

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