Alkylsilanes structure

Figure 5. Schematic structure of a polysiloxane layer obtained by hydrolysis and poly condensation of monomeric alkylsilanes RSiX3 (X = Cl, OCH3, OC2H5).

The chemistry of silicone halides was recently reviewed by Collins.13 The primary use for SiCU is in the manufacturing of fumed silica, but it is also used in the manufacture of polycrystalline silicon for the semiconductor industry. It is also commonly used in the synthesis of silicate esters. T richlorosilane (another important product of the reaction of silicon or silicon alloys with chlorine) is primarily used in the manufacture of semiconductor-grade silicon, and in the synthesis of organotrichlorosilane by the hydrosilylation reactions. The silicon halohydrides are particularly useful intermediate chemicals because of their ability to add to alkenes, allowing the production of a broad range of alkyl- and functional alkyltrihalosilanes. These alkylsilanes have important commercial value as monomers, and are also used in the production of silicon fluids and resins. On the other hand, trichlorosilane is a basic precursor to the synthesis of functional silsesquioxanes and other highly branched siloxane structures. 

F) K.K. Andreev, "Termicheskoye Razlo-zheniye i Goreniye Vzryvchatykh Veshchestv (Thermal Decomposition and Combustion of Explosive Substances), GosEnergoIzdat, Moscow(1957) G) P. Breisacher et al, "Flame Front Structure of Lean Diborane-Air and Diborane-Hydrocarbon-Air Mixtures", 7thSympCombstn(1959), PP 894-902 H) M. Getstein, "A Study of Alkylsilane Flames , Ibid, pp 903-05 I) P.L. Harrison, "The Combustion.of Titanium and Zirconium , Ibid, pp 913-20 J) J.D. Lewis A.C, Merrington, "Combustion of n-Heptane Spray in the Decomposition Products of Concentrated Hydrogen Peroxide , Ibid, pp 953-57... 

Acid catalysis—hydrolysis. Several series of alkylsilane esters were studied to determine the effect of silane structure on the hydronium ion catalyzed hydrolysis reaction. The hydronium ion catalyzed hydrolysis rate constants for a series of alkyl tris-(2-methoxyethoxy)silanes in aqueous solution were used to define the modified Taft equation log(A /Ah ) = 0.39a + 1.06ES, where Ho is the rate of hydrolysis for methyl tris-2-(methoxyethoxy)silane [42], The hydronium ion catalyzed hydrolysis rate constants and the reaction half-lives are reported in Table 2. In a similar manner, the hydronium ion catalyzed hydrolysis rate constants for a series of trialkylalkoxysilanes in 55% aqueous acetone were used to obtain the modified Taft equation log(/cH//cHo) = -0.37 a + 2.48 E where kHo is the rate of hydrolysis for trimethylalkoxy-silane. 

When alkylsilanes such as methylsilane, dimethylsilane, trimethylsilane, tetra-methylsilane, and hexamethyldisilane polymerize in a glow discharge, the stoichiometry, chemical structure, and properties of the resulting polymers generally depend on the discharge conditions (2, 8, 21, 22], Elemental compositions from XPS for plasma trimethylsilane polymers deposited under different... 

IR, UV and, most importantly, NMR spectroscopy have proven to be excellent tools for elucidation of the molecular and electronic structures of silyl anions. Whereas 13C NMR data of metalated alkylsilanes are quite rare, the wealth of 13C NMR data which are available for metalated arylsilanes allows one to draw important conclusions concerning the question of charge delocalization in these compounds (Table 2)36,47. 

Molecular and structural characteristics of methoxysilane SA-layers deposited on inorganic subtrates can be obtained using DRIFT spectroscopy in combination with TOF-SIMS. The hydrolysis rates are strongly influenced by the acid/base properties of the oxide surface. In accord to this, the contribution of residual Si-OCHs units is much lower for SA-layers on the basic alumina. The outmost layers of the polysiloxanes consist of completely hydrolyzed species. In case of methylsilanes, the SIMS spectra indicate the presence of T and T OH silsesquioxanes whereas for higher alkylsilanes the formation of T OH isomers is likely. This hypothesis has to be addressed in future studies with particular focus on structural aspects. 

The technique for generating such structures comprises the formation of a molecular gradient of a polymerization initiator on the solid substrate and subsequent polymerization from the substrate-bound initiators.58-60 For this purpose, one of the alkylsilane components is terminated by the initiator moiety. Gradient polymer brushes can be engineered if the binary monolayer is terminated by two different polymerization initiators (Fig. 3.4).61... 

Kupchik, E.J. (1985) Structure-molar refraction relationships of alkylsilanes using molecular cormectivity. Quant. Struct. -Act Relat, 4,123-127. 

An investigation of poly(di- -alkylsilane)s with short side chains assumes a critical importance for a generalized understanding of the structures, energetics and phase transition of this novel class of polymers. The structures of the poly(di-n-alkylsilane) family are far more complicated than presumed to date, requiring a re-examination of our current understanding of the structure-property relationships of these important polymers. 

L. H. Hall and D. Aaserud, Quant. Struct.-Act. Relat., 8, 196 (1989). Structure-Activity. Models for Molar Refraction of Alkylsilanes Based on Molecular Connectivity. 

Alcohol- or water-producing condensation generates a three-dimensional network. Pohl and Osterholtz (6) showed that condensation of alkylsilane-triols is specific acid and base catalyzed. Above the isoelectric point of silica (about pH 2.5) condensation proceeds by nucleophilic attack of deprotonated silanols on neutral silicates (6, 23). Below the isoelectric point the reaction proceeds by protonation of silanols followed by electrophilic attack (2, 6). These reactions favor less highly condensed sites, because these are the most electron rich, and lead to more extended, ramified structures. Above pH 2.5, reactions favor more highly condensed sites. 

To assemble the surface-bound membrane structure, we first form a hydrophobic monolayer by using alkylsilanization to covalently attach long-chained hydrocarbon chains to hydroxyl groups in the oxide layer on the electrode surface. Such a hydrophobic surface can be thought of as one leaflet of a membrane bilayer. Alkylsilane-modified surfaces have been widely used as substrates for lipid monolayers deposited by Langmuir-Blodgett techniques. The lipids in these monolayers have mobilities like those of lipids... 

We simultaneously incorporate both lipid and protein by using dialysis to remove detergent from a solubilized lipid-protein mixture in the presence of the alkylsilanated substrate. Under our conditions, from the evidence in this paper and elsewhere (9), the surface structures appear to be single bilayer membranes. Our hypothesis is that the hydrocarbon chains attached to the surface serve as initiation sites for a lipid bilayer membrane to form as the detergent is slowly removed. The model is of a membrane that is anchored to the surface by hydrophobic interactions with the surface-bound hydrocarbon layer. Integral membrane proteins are retained in these structures by their interaction with the hydrophobic core of the membrane without being directly attached to the electrode surface. 

Electrochemical impedance spectroscopy provides a sensitive means for characterizing the structure and electrical properties of the surface-bound membranes. The results from impedance analysis are consistent with a single biomembrane-mimetic structure being assembled on metal and semiconductor electrode surfaces. The structures formed by detergent dialysis may consist of a hydrophobic alkyl layer as one leaflet of a bilayer and the lipid deposited by dialysis as the other. Proteins surrounded by a bound lipid layer may simultaneously incorporate into pores in the alkylsilane layer by hydrophobic interactions during deposition of the lipid layer. This model is further supported by the composition of the surface-bound membranes and by Fourier transform infrared analyses (9). 

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