Alkoxides solutions

Deactivation in the anion formed under the reaction conditions prevents alkoxy-dechlorination of 4-chloro-2-quinolone (222) with boding alkoxide solution while 4-chloroquinoline and its 2-ethoxy and 2-anilino derivatives react. 4-Chloro-iV -methyl-2-quinolone reacts readily. 

It was shown (1-3) that the silicon alkoxide solutions become spinnable when an acid is used as catalyst and the water content of the starting solution is small at less than 4 or 5 in the water to silicon alkoxide molar ratio. Recently, it has been found that this rule for the possibility of drawing fibers is only valid for the solutions reacted in the open system and no spinnability is found in the solutions reacted in the closed system (4). It has also been found that the addition of very large amounts of acid to the starting solution produces relatively large round-shaped particles, preventing the occurrence of spinnability (4). These will be discussed in the first half of this paper. 

Further examination into the factors affecting the drawability of the alkoxide solution... 

It has been shown that the spinnability occurs in the silicon alkoxide solution when an acid is used as catalyst and the water content is small at less than 4 in the water to metal alkoxide ratio. 

So far the results have been shown in which the metal alkoxide solutions are reacted in the open system. It has been shown that the metal alkoxide solutions reacted in the closed container never show the spinnability even when the starting solutions are characterized by the low acid content and low water content (4). It has been also shown from the measurements of viscosity behavior that the solution remains Newtonian in the open system, while the solution exhibits structural viscosity (shear-thinning) in the closed system. 

The electrochemical deposition of doped silica, ORMOSIL and related nanocomposite thin films at the surface of electrodes is opening a whole new field of applications. In the latter case, a potential is applied to an alkoxide solution which alters the pH on the electrode surface and thus enhances the rate of condensation.40 The resulting single-step... 

Randon et al. reported on an alternative approach for the preparation of zirconia monoliths [96]. The sol-gel process is initiated by hydrolysis of an ethanolic zirconium alkoxide solution, on addition... 

In 1956 Gerhard Kolbe (1) published the first results that showed that spherical silica particles could be precipitated from tetraethoxysilane in alcohol solutions when ammonia was present as the catalyzing base. Several years later, in 1968, StOber, Fink, and Bohn (2) continued in this research area and published the frequently cited original article for the preparation of monodispersed silica particles form alkoxide solutions. StOber et al. improved the precipitation process and described the formation of exceptionally monodispersed silica particles. The final particle size could be controlled over a wide range from about 50 nm to 1 1/2 p,m. Variations of the particle size could be achieved by different means, e.g., temperature, water and ammonia concentration, type of alcohol (solvent), TEOS (tetraethoxysilane) concentration, or mixing conditions. 

When multicomponent alkoxide solutions, or a single alkoxide and a soluble inorganic salt, are mixed, a multicomponent alkoxide may result. In this way, such complex oxides such as the YBCO superconductor (cf. Section 6.1.2.4) can be formed. Sol-gel processing can also be used to coat fibers for composites and to form ceramics with very fine pore sizes called xerogels. A xerogel commonly contains 50-70% porosity, a pore size of 1-50 nm, and a specific surface area exceeding 100 m /g. 

For secondary or tertiary alcohols, the yields are improved by adding the alcohol-alkoxide solution dropwise to a solution of trichloroacetonitrile and ethyl ether at 0°. 

A. Lithium triethylcarboxide (Solution 1). A thoroughly dried, 1-1., three-necked, round-bottomed flask is fitted with a septum inlet with serum cap, a reflux condenser, and a magnetic stirrer. The flask is purged with and maintained under an atmosphere of dry nitrogen. A solution of 300 ml. of 1.66 M butyllithium (0.50 mole) in hexane (Note 1) is introduced into the flask by syringe (Note 2) and cooled to 0° in an ice bath. Then 58 g. (0.50 mole) of 3-ethyl-3-pentanol (Note 3) is added slowly but constantly by syringe (Note 4). At the end of addition the yellow tint of the butyllithium solution disappears. The alkoxide solution is standardized by hydrolysis of aliquots in water and by titration of the resulting lithium hydroxide with standard acid to a phenol-phthalein end point (Note 5). 

Co-precipitation in Aqueous Medium - Despite its effectiveness, the alkoxide method presents some drawbacks for industrial scale-up the high cost of the starting reactants and the requirement for water-free and oxygen-free environment for the alkoxide solutions. 

The electrochemical technique can be used also for direct synthesis of bimetallic alkoxides. For instance, the anodic dissolution of rhenium in the methanol-based electrolyte that already contained MoO(OMe)4, permitted to prepare with a good yield (60%) a bimetallic complex RevMov,02(OMe)7, with a single Re-Mo bond [904], Application of the same procedure permitted the preparation of complex alkoxide solutions with controlled composition for sol-gel processing of ferroelectric films [1777]. 

Application of halogenides under the same conditions results inMHal/OR), which does not decompose in excess of M OR or under refluxing. The patent [833] describes the general method of preparation of the stable metal alkoxide solutions (which are used in technology) it comprises a heterogeneous reaction of Zn, Cd, Y, Ln, In, Pb, Sn, Zr, Sb, Bi and Mn carboxylates in alcohol solutions with NH3 or amines with subsequent purification by ionic exchange. 

Condensation of metal alkoxides occurring as a result ofuncontrolled hydrolysis greatly influences further hydrolysis therefore, the properties of the products are highly dependent on the content of residual water in the anhydrous solvents used for the preparation of metal alkoxide solutions, as well as on the time and conditions of storage of the solutions prior to hydrolysis. This fact was demonstrated by the study of hydrolysis of Zr(OR)4, which are especially sensitive to water [1015],... 

Aluminum oxide sols are successfully used for application of films [1794, 1793], such as high area films for hybrid circuits [1236]. The same technique was used for the preparation of J-A1203 (NaAlnO,7) in this case alcoholic solutions of NaOR were added to aluminum alkoxide solutions [1795, 1038]. To increase the stability of sols, aluminum alkoxides are frequently modified with acetic acid [1570] or (3-diketones [1659]. Alumina sheets are commercially produced by the sintering of high-purity fine A1203 powders prepared by hydrolysis of modified Al(OPr )3 [1236]. To prepare powders with spherical species from dilute solutions, hydroxopropylcellulose was added to prevent... 

Crystalline BaTi03prepared by hydrolysis of the alkoxide solutions in the form of dispersion without drying was successfully used to make a ceramic slip formulation, which was then cast as a ceramic green body for microcapacitors 1 to 50 pm thick. 

In [1677] complex alkoxides and alkoxide-carboxylates were compared as precursors for preparation ofBST films. In contrast to the introduction of alkaline earth carboxylates in the form of preliminary isolated salts, in this work metal alkoxide solution in methoxyethanol containing titanium and alkaline-earth metal was modified by addition of 2-ethylhexanoic acid with subsequent slow distilling off the solvent and repeated dilutions with fresh portions of methoxyethanol. During the distillation process, part of the alkoxide groups are substituted by the 2-ethylhexanoate ligands. The exchange reaction of Ti(OPr )4 with acid was studied in different solvents, and it was demonstrated that in the course of distillation the titanium oxoisopropoxy-2-ethylhexanoate is formed with elimination of ester ... 

Oxoalkoxocomplexes are oligomers of varying molecular complexity. The extent and conditions of distillation allow to control the nature of the species in solution, thus influencing the film-formation process [1368], This process of in situ modification ofmetal alkoxide solution by carboxylate ligand may have certain advantages with respect to the chemical uniformity as compared to the techniques based on simple mixing of a titanium alkoxide with alkaline-earth carboxylates. 

IR spectra measurements as well as variation of the film thickness, shrinkage, and refractive index demonstrated substantial differences in the mechanisms of thermal decomposition of films prepared from the exclusively metal alkoxide precursor and from the metal alkoxides modified by 2-ethylhexanoic acid. These differences affect the evolution of film microstructure and thus determine the different dielectric properties of the obtained films. The dielectric permittivity of the films prepared from metal alkoxide solutions was relatively low (about 100) and showed weak dependence ofthe bias field. This fact may be explained by the early formation of metal-oxide network (mostly in the... 

Shut off all possible sources of ignition. Wear face shield, goggles, laboratory coat, and butyl rubber gloves. Cover spill of alkoxide solution with a 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand. Transfer to a pail of water in the fume hood. Neutralize the solution with 6 M hydrochloric acid (prepared by cautiously adding concentrated acid to an equal volume of cold water). Decant liquid to drain with at least 50 times its volume of water. Solid residue may be... 

Instead of a steam bath or a water bath, an electrically heated oil bath is suitable. This permits easy regulation of the rate of distillation. However, the temperature of the bath should not exceed 95-100° when isopropyl alcohol is the solvent if possible dehydration of a sensitive alcohol is to be avoided. For this same reason, a burner, hot plate, or sand bath is not recommended for heating. Especially at the end of the reduction, superheating of the concentrated alkoxide solution may bring about dehydration or other decomposition of the product. 

Tellurium Tetra[isopropoxide]3 4 10 g (37 mmol) of tellurium tetrachloride are dissolved in 20 ml of isopropanol and 3.4 g (148 mmol) of sodium are added to a further 50 ml of isopropanol. When all the sodium has reacted, the alkoxide solution is added dropwise to the ice-cooled tellurium tetrachloride solution. When the exothermic reaction has subsided, the mixture is diluted with benzene, heated under reflux for 1 h, and the solvent is distilled off. The residue is kept under reduced pressure at 20° to completely remove all volatile substances and the resultant residue is fractionally distilled under vacuum yield 6.5 g (50%), b.p. 76°/0.5 torr. 

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