Sodium condensation method

This method depends on the reaction of an organic chloride with silicon tetrachloride in the presence of sodium, lithium or potassium. 

This reaction, based on the Wurtz reaction, tends to go to completion and the yield of technically useful chlorosilane is low. 

The commercial value of this method is also limited by the hazards associated with the handling of sodium. 

Several techniques have been devised which provide convenient methods of converting by-product chlorosilanes into more useful intermediates. A typical example, valuable in technical-scale work, is the redistribution of 

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Similar reactions can also be written for the alkoxysilanes but in commercial practice the chlorosilanes are favoured. These materials may be prepared by many routes, of which four appear to be of commercial value, the Grignard process, the direct process, the olefin addition method and the sodium condensation method. 

The polyorganosiloxanes are generally prepared via chlorsilanes which are hydrolyzed to give hydroxyl compounds and which in turn condense to form polymers. Several methods are available for the production of the chlorsilane intermediates including the Grignard method, the Rochow direct process, the olefin addition method, the sodium condensation method and certain rearrangement techniques. 

Another condensation method was investigated by Carothers and co-workers and reported in 1930. They reacted decamethylene dibromide with sodium in a Wurtz-type reaction but found it difficult to obtain polymers with molecular weights above 1300. 

C. Diazomethane. Sodium cyclohexoxide method (Note 10). A solution of sodium cyclohexoxide is prepared from 4 g. of sodium and 100 ml. of cyclohexanol (Note 11) in a 2-1. flask the cyclohexanol is heated to boiling under reflux to speed up the formation of the alkoxide. As soon as the sodium has disappeared, heating is discontinued and the condenser is removed. When solid begins to separate from the solution, the mixture is stirred with a stout rod to prevent the formation of a hard cake. The flask is surrounded by an ice bath, and, when the temperature of the mixture has dropped to 10°, 300 ml. of dry ether and a solution of 49 g. (0.33 mole) of N-nitroso-j8-methylaminoiso-butyl methyl ketone dissolved in 600 ml. of dry ether are added. The flask is connected to a 25-cm. fractionating column and an efficient water-cooled condenser (Note 12). The delivery end of the condenser should be connected to an adapter which dips below the surface of 50 ml. of ether contained in a 1-1. Erlenmeyer... 

Diisopropyl Ditellurium [Sodium Hydride Method]2 A 500 ml flask fitted with a magentic stirrer and a reflux condenser is purged with nitrogen and charged with 15.0g (0.11 mol) of tellurium and 100 m/ of dimethylformamide (freshly distilled from calcium chloride). 5.64 g of a 50% suspension of sodium hydride (0.11 mol) in mineral oil are added, the mixture is slowly heated over 1 h to 70° with stirring on a water bath, maintained at this temperature for 3 h, and then allowed to cool to 20°. 14.50 g (0.11 mol) of isopropyl bromide are added dropwise over 30 min, the mixture is stirred for 30 min, poured into 200 ml of water, and extracted with three 25 ml portions of chloroform. The combined extracts are washed with three 25 ml portions of distilled water, dried with anhydrous calcium chloride, and the solvent removed under aspirator vacuum. The residue is purified by chromatography on silica gel with hexane as the mobile phase yield 13.5 g (72%) b.p. 92°/2 torr. 

The sodium condensation reaction of a,co-bis(chlorosilyl)-substituted compounds and the coupling reaction of dilithio derivatives of compounds bearing 7t-electron systems with dichlorosilanes offer a convenient route to various silicon containing polymers. However, the polymers prepared by these methods always contain a small proportion of siloxy units in the polymer backbone, which would interrapt the electron delocalisation. Therefore, new synthetic routes to organosilicon polymers have been developed in which no alkali metal halide condensations are involved [6, 7]. We report syntheses of organosilicon... 

The condensation method begins with molecular units, and the particles are built-up by a process of nucleation typical example is the preparation of polymer lattices, in which case the monomer (e.g., styrene or methylmethacrylate) is emulsified in water using an anionic or nonionic surfactant (e.g., sodium dodecyl sulphate or alcohol ethoxylate). A polymeric surfactant is also added to ensure the long-term colloid stabiHty of the resulting latex. An initiator such as potassium persulphate is then added and, when the temperature of the system has increased, initiation occurs that results in formation of the latex [polystyrene or poly(methylmethacrylate)]. 

In addition to the conventional sodium hydride method of anion generation, organolithium compounds 50% aqueous sodium hydroxide in acetonitrile and 50% sodium hydroxide with a phase transfer catalyst have been used to generate the anion of Reissert compounds for condensation with aldehydes. A variety of substituted benzaldehydes have been allowed to react with anions of type 26 to give45. ° - ... 

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