Dimethyldichlorosilane, reaction

Dimethyl a-chloro-/3-phenyl-succinate, 222 Dimethyldichlorosilane, reaction with polyesters, 491... 

The purity of the product was determined by the checkers by GLC analysis using the following column and conditions 3-nm by 1.8-m column, 5% free fatty acid phase (FFAP) on acid-washed chromosorb W (60-80 mesh) treated with dimethyldichlorosilane, 90 C (1 min) then 90 to 200 C (15°C per rain). The chromatogram showed a major peak for methyl 2-methyl-l-cyclohexene-l-carboxylate preceded by two minor peaks for methyl 1-cyclohexene-l-carboxylate and l-acetyl-2-methylcyclohexene. The areas of the two impurity peaks were 5-6% and 0.5-2% that of the major peak. The purity of the product seems to depend upon careful temperature control during the reaction. The total amount of the two impurities was 14-21% in runs conducted at about -15 to -20°C or at temperatures below -23°C. 

Under the most favourable reaction conditions when methyl chloride is used the crude product from the reaction tube will be composed of about 73.5% dimethyldichlorosilane, 9% trichloromethysilane and 6% chlorotrimethylsilane together with small amounts of other silanes, silicon tetrachloride and high boiling residues. 

Difunctional reagents, for example the very cheap dimethyldichlorosilane 48, which is produced on a large technical scale, and the much more reactive and expensive dimethylsilyl bis(O-triflate) 49 [65-67] (Scheme 2.8) convert alcohols or phenols 11 in the presence of bases, for example triethylamine or DBU, into the silylated compounds 50. Thus 48 and 49 and other bifunctional reagents such as di-tert-butyldichlorosilane [68] or di(tert-butylsilyl)-bis(0-triflate) [69] and the subsequently described 51 and 52 combine two alcohols to silicon-tethered molecules 50, which can undergo interesting intramolecular reactions [70-74]. 

As already discussed in Section 2.2, crystalline dimethylsilanediol 53 can be prepared by hydrolysis from hexamethylcyclotrisilazane 51, from dimethoxydimethyl-silane [40], and from octamethylcyclotetrasilazane (OMCTS) 52. The most simple preparation of 53 is, however, controlled hydrolysis of dimethyldichlorosilane 48 in the presence of (NH4)2C03 or triethylamine [41]. Likewise, hydrolysis of hexam-ethylcyclotrisiloxane 54 and of octamethylcyclotetrasiloxane 55 eventually gives rise to dimethylsilanediol 53. In all these reactions the intermediacy of the very reactive dimethylsilanone 110 has been assumed, which can be generated by pyrolytic [42, 43] and chemical methods [44—46] and which cyclizes or polymerizes much more rapidly, e.g. in contact with traces of alkali from ordinary laboratory or even Pyrex glassware [40, 47] to 54, 55, and 56 than trimethylsilanol 4 polymerizes to hexamethyldisiloxane 7. Compound 111 is readily converted into dimethylsilanone 110 and MesSil 17 [46] (Scheme 3.6). 

Thus we hope that these O-silylations-activations with the readily available HMDS (MesSiNHSiMes), TCS (MesSiCl), dimethyldichlorosilane (Me2SiCl2), hexa-methylcyclotrisilazane (HNSiMe2)s, OMCTS (HNSiMe2)4, tetra(alkoxy) silane (Si(OR)4) or sihcon tetrachloride (SiCL ), most of which can also effect the transient protection of any present hydroxyl group, and the subsequent or concomitant reaction with nucleophiles accompanied by formation of silylated water as HMDSO (MesSiOSiMes), (OSiMe2)n or Si02 will be applied more often in the fu-... 

Organosilanes, especially dimethyldichlorosilane (M2), are important chemicals used in the silicone industries. The direct reaction of silicon with an organic halide to produce the corresponding organosilanes as a gas-solid-solid catalytic reaction was first disclosed by Rochow [1]. In the reaction, a copper-containing precursor first reacts with silicon particles to form the catalytically active component, which is a copper-silicon alloy, the exact state of which is still under discussion. As the reaction proceeds. Si in the alloy is consumed, which is followed by the release of copper. This copper diffuses into the Si lattice to form new reaction centers until deactivation occurs. The main reaction of the direct process is ... 

The principal dichlorides used in this study were hexylmethyl-dichlorosilane (HMDS) and phenylmethyldichlorosilane (PMDS), some copolymerizations of the latter and dimethyldichlorosilane (DMDS) were also made. The usual practice was to add the dichloride (20 vol.%) in one portion to the refluxing reaction mixture at the start of the reaction. This usually entailed cooling the reaction mixture when PMDS was used to prevent a too vigorous reflux at the beginning of the reaction. In all cases the reaction turned dark purple and ultimately viscous. 

The most important process so far has been the reductive elimination of halogens with the formation of Si-Si bonds. Kipping used this reaction and discovered the first perphenylated cyclosilanes, yielding polysilanes as a by-product [8]. Similarly dodecamethylcyclohexasilane was found using dimethyldichlorosilane as a starting material for this reaction by Burkhardt in 1949, but 90% of the yield appeared as poly silane by-products [9]. 

The discussion continues regarding the role of silanone and cyclodisiloxanes as reactive intermediates in the formation of Si-O-Si bond.25 In studies of the reaction of dimethyldichlorosilane, phenylmethyldichlorosilane, or diphenyldichlorosilane with dimethyl sulfoxide in the presence of 2,2,5,5-tetramethyl-l-oxa-2,5-disilacyclopentane, Weber and co-workers obtained products of the insertion of diorganosiloxy unit into the cyclic siloxane, accompanied... 

Methyltrichlorosilane is produced by the Grignard reaction of silicon tetrachloride and methylmagnesium chloride (structure 17.24). Dimethyldichlorosilane, used in the synthesis of polydimethylsiloxane, is obtained by the reaction of methylmagnesium chloride and methyltrichlorosilane (structure 17.25). 

The fact that the difunctional dimethyldichlorosilane had no effect on the flow time of the polyisoprenyl lithium offers perhaps the most convincing evidence that these chain ends must have been associated in pairs prior to the linking reaction. The corresponding values provide the necessary confirmation that the linking reaction has actually taken place. It should also be noted that flow times of the terminated linked polymers can also be used to detect the presence of some unlinked, but associated, chains. 

Another way of synthesizing B-A-B triblock copolymers is to use a coupling reaction.2 Monocarbanionic poly-B precursor is used to initiate the polymerization of A. The living two block copolymer is then reacted stoichiometrically with an efficient bifunctional coupling agent, such as dibromo-p-xylene or dimethyldichlorosilane, or even phosgene. This coupling reaction yields the triblock copolymers. 

The reaction of pure silica MCM-48 with dimethyldichlorosilane and subsequent hydrolysis results in hydrophobic materials with still a high number of anchoring sites for subsequent deposition of vanadium oxide structures. The Molecular Designed Dispersion of VO(acac)2 on these silylated samples results in a V-loading of 1.2 mmol/g. Spectroscopic studies evidence that all V is present as tetrahedral Vv oxide structures, and that the larger fraction of these species is present as isolated species. These final catalysts are extremely stable in hydrothermal conditions. They can withstand easily hydrothermal treatments at 160°C and 6.1 atm pressure without significant loss in crystallinity or porosity. Also, the leaching of the V in aqueous conditions is reduced with at least a factor 4. 

A water-methylene dichloride mixture is satisfactory as a hydrolyzing agent on groups of compounds such as phenyltrichlorosilane, dimethyldichlorosilane and melhyltnchlorosilane. The value of higherboiling ethers lies in their ability to provide higher-boiling reaction systems. 

The mixture of chromium trioxide with one equivalent of trimethylsilyl chloride, with no solvent added, results in the formation of an explosive red liquid that is soluble in dichloromethane or tetrachloromethane.428 It is suggested, with no spectroscopic evidence, that it consists of trimethylsilyl chlorochromate [Me3Si-0-Cr(0)2-Cl]. This compound, which can safely be used in organic solvents, is able to oxidize alcohols to aldehydes or ketones, and interacts with r-butyldimethylsilyl ethers producing deprotection, followed by oxidation of the liberated alcohol.138 Compounds analogue to trimethylsilyl chlorochromate are also able to oxidize alcohols, although they possess lesser reactivity. They can be prepared by reaction of chromium trioxide with dimethyldichlorosilane and diphenyldichlorosilane.428b... 

The direct reaction of methyl chloride with silicon metal is the foundation stone of the worldwide silicone industry352. In corporate laboratories over the years, the reaction has been carefully engineered to provide the maximum amount of the desired product, dimethyldichlorosilane. Despite the industrial importance of the direct reaction, and the great amount of research devoted to it, its mechanism is still obscure353. Recently, however, a model has been suggested in which silicon in silylene form provides the crucial intermediate. 

A variation of the preparative method for octamethyltrisilane (XIII n=3) involves the reaction of dimethyldichlorosilane with lithium in the presence of a large excess of trimethylchlorosilane in tetrahydrofuran (60). The yields of the trisilane are good ( 65%), and small amounts of the next two higher homologs also are obtained. An advantage claimed for this procedure is that it is a one-step synthesis employing commercially available materials. 

Three permethylated cyclosilanes of the formula [(CH3)2Si]B with n=5-7 are prepared by allowing dimethyldichlorosilane to react with sodium-potassium alloy in tetrahydrofuran. From this reaction, an insoluble polymeric mass and a crystalline solid are produced (21, 177). The latter consists, for the most part, of dodecamethylcyclohexasilane but it also contains decamethylcyclopentasilane and tetradecamethylcycloheptasilane in small quantities. The amounts of both five- and seven-membered cyclosilanes are much increased if the reaction is worked up immediately after the addition of the dichlorosilane is completed with little or no refluxing. The three cyclosilanes can be separated by preparative gas chromatography 21). 

An interesting silacycloalkane containing silicon-silicon bonds in the ring (XVII) has been obtained by introducing isobutylene into a reaction mixture of dimethyldichlorosilane and lithium metal in tetrahydrofuran at 0°-10° C (137). 

The reaction of dimethyldiethoxysilane ((CHj SftOQHj) with the isolated silanols proceeds under milder conditions than the chlorosilane analogue dimethyldichlorosilane ((CH3)2SiCl2). 

---