Chlorosilane compounds

There are two gereral routes to mikto-arm star polymers. The first method makes use of the stepwise addition of living polymers to multifunctional chloro-silane compounds [59-62], The Athens group uses the sequential addition of living polymers to multifunctional chlorosilane compounds under tight stoichiometric control [63, 64],... 

Their advantage over other types of dendrimers is their straightforward synthesis and, most importantly, their chemical and thermal stabilities. Two distinct steps characterize their synthesis a) an alkenylation reaction of a chlorosilane compound with an alkenyl Grignard reagent, and b) a Pt-cata-lyzed hydrosilylation reaction of a peripheral alkenyl moiety with an appropriate hydrosilane species. Scheme 2 shows the synthesis of catalysts Go-1 and Gi-1 via this methodology. In this case, the carbosilane synthesis was followed by the introduction of diamino-bromo-aryl groupings as the precursor for the arylnickel catalysts at the dendrimer periphery. The nickel centers of the so-called NCN-pincer nickel complexes were introduced by multiple oxidative addition reactions with Ni(PPh3)4. 

A better way to synthesize star molecules with a precisely defined number of arms is the deactivation of the living arms with an electrophilic linking agent (usually a chlorosilane compound) having the desired number of reactive bonds, equal to the target functionality of the star-block copolymer. Chlorosilane compounds with numbers of Si-Cl bonds ranging from 3 to 18 have been employed, giving star-block copolymers with controlled functionalities [16] (Scheme 2). 

Most applications of liquid column chromatography are now made on silica which has been chemically modified (bonded phase chromatography). The modification is made by chemical reaction between the silanol groups and a chlorosilane compound. The carbon radicals of the chlorosilane compound determines the nature of the final column material. Using silanes containing alkyl carbon chains with 8-22 carbon atoms gives the particles hydrophobic surfaces, but more polar surfaces may be obtained by incorporation of alcohol, amino, cyano or other groups in the alkyl chain. 

There are two basic routes for the commercial preparation of silane. The first involves the acid hydrolysis of magnesium silicide (Mg2S ) to give a mixture of silicon hydrides, which are then separated by fractional distillation. The second method involves the direct or indirect reduction of chlorosilane compounds with hydrogen to give silane. Further purification is generally necessary [11]. 

On the other hand, the (AB) star copolymers were prepared by the condensation of AB diblock anions using chlorosilane compound [59]. This star copolymer could also be synthesized by crosslinking diblock monocarbanionic [60,61] or monocarbocationic chains [62,63] with bis-unsaturated monomers. 

The reaction of lithiated cumulenic ethers with ethylene oxide, trimethyl-chlorosilane and carbonyl compounds shows the same regiosnecificity as does the alkylation. 

PEROXIDES AND PEROXIDE COMPOUNDS - ORGANIC PEROXIDES] (Vol 18) t-Butyl diphenyl chlorosilane... 

Direct Process. Passing methyl chloride through a fluidized bed of copper and siUcon yields a mixture of chlorosilanes. The rate of methylchlorosilane (MCS) production and chemical selectivity, as determined by the ratio of dimethydichlorosilane to the other compounds formed, are significantly affected by trace elements in the catalyst bed very pure copper and siUcon gives poor yield and selectivity (22). 

Many chlorine compounds, including methyl chlorosilanes, such as ClSi(CH2)3, Cl2Si(CH3)2, Cl3Si(CH3) tetrachlorosilane [10026-04-7] SiCl chlorine, CI2 and carbon tetrachloride, CCl, can completely react with molecular surface hydroxyl groups to form hydrochloric acid (40), which then desorbs from the gel body in a temperature range of 400—800°C, where the pores are still interconnected. Carbon tetrachloride can yield complete dehydration of ultrapure gel—siUca optical components (3,23). 

The polyorganosiloxanes are generally prepared by reacting chlorosilanes with water to give hydroxyl compounds which then condense to give the polymer structure, e.g. 

Table 29,1 Boiling point of some chlorosilanes and related compounds...

Silylnitronates 1 are prepared14-24,25 by metalation of primary nitroalkanes with lithium diisopropylamide and treatment of the lithionitronates with either chlorotrimethylsilane or (/er/-butyldimethyl)chlorosilane. Nonaqueous workup and distillation gives the silylnitronates in >75% yield as moisture sensitive, but thermally stable, products. (e/7-Butyldimethylsilylni-tronates are more stable than the corresponding trimethylsilyl compounds. 

Metal-induced reductive dimerization of carbonyl compounds is a useful synthetic method for the formation of vicinally functionalized carbon-carbon bonds. For stoichiometric reductive dimerizations, low-valent metals such as aluminum amalgam, titanium, vanadium, zinc, and samarium have been employed. Alternatively, ternary systems consisting of catalytic amounts of a metal salt or metal complex, a chlorosilane, and a stoichiometric co-reductant provide a catalytic method for the formation of pinacols based on reversible redox couples.2 The homocoupling of aldehydes is effected by vanadium or titanium catalysts in the presence of Me3SiCl and Zn or A1 to give the 1,2-diol derivatives high selectivity for the /-isomer is observed in the case of secondary aliphatic or aromatic aldehydes. 

In this section, the reactivities of organosilicon compounds for the Friedel-Crafts alkylation of aromatic compounds in the presence of aluminum chloride catalyst and the mechanism of the alkylation reactions will be discus.sed, along with the orientation and isomer distribution in the products and associated problems such as the decomposition of chloroalkylsilanes to chlorosilanes.. Side reactions such as transalkylation and reorientation of alkylated products will also be mentioned, and the insertion reaction of allylsilylation and other related reactions will be explained. 

To optimize the alkylation conditions, ferrocene was reacted with allyldimethyl-chlorosilane (2) in the presence of various Lewis acids such as aluminum halides and Group lO metal chlorides. Saturated hydrocarbons and polychloromethanes such as hexane and methylene chloride or chloroform were used as solvents because of the stability of the compounds in the Lewis acid catalyzed Friedel-Crafts reactions. The results obtained from various reaction conditions are summarized in Table IV. 

To prepare multifunctionalized symmetric organosilicon compounds by the polyalkylation of benzene. (2-chloroethyi)trichlorosilane and (3-chloropropyl)tri-chlorosilane were reacted with benzene. Polyalkylations of benzene with (2-chloroethyl)silane and (3-chloropropyl)silane were carried out in the presence of aluminum chloride catalyst at a reaction temperature of 80 C. The reaction of benzene with excess (2-chloroethyI )trichlorosilanes afforded pcralkylated product, hexakis(2-(trichlorosilyl)ethyl)benzene in good yield (70%). ... 

Reaction of tert-butyldimethylsilanol 85 a or tert-butyldiphenylsilanol 85 b, which are obtained on cleavage of O-silyl compounds, with SOCI2 in CHCI3, affords the desired re-usable chlorosilanes 86a and 86b in 39 and 81% yield, respectively [109] (Scheme 2.16). 

In Section 3 of this chapter it was mentioned that polymers obtained by intermolecular condensation of bifunctional monomers may often be prepared alternatively by an addition polymerization of a cyclic compound having the same composition as the structural unit. Typical examples are shown in Table III. The processes indicated are appropriately regarded as addition polymerizations. Each of these polymers may also be prepared through the condensation of suitable bifunctional monomers. The dimethylsiloxane polymer, for example, may be prepared, as indicated in Table I (p. 45), through the condensation of dimethyl dihydroxysilane formed by hydrolysis of the di-chlorosilane... 

Tetrachlorosilane was added to aqueous ethanol (the presence of water was accidental). There was no proper stirring during this operation, which led to the formation of two liquid layers of compounds that did not react. The very fast and exothermic reaction of the alcoholysis-hydrolysis of chlorosilane started violently and the large compoundion of hydrogen chloride caused the reactor to detonate. 

An important reaction of silicon compounds containing electronegative substituents, such as the halogens or a Group 15 or 16 element, is hydrolysis, which often occurs very readily even with atmospheric moisture. The primary reaction in silicone production is the hydrolysis of halosilanes, usually the readily available chlorosilanes, to give silanols, which then undergo acid-catalyzed condensation with loss of water, as shown in Scheme 1. 

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