Compounds silicon

Silicon compounds have been extensively explored in ADMET chemistry [104]. A variety of sihcon compounds are amenable to ADMET conditions, and a number of carbosilane backbones have been synthesized. 

The first attempt at ADMET polymerization of a silane diene, specifically dimethyldivinylsilane, was unsuccessful [20]. This was presumably due to the unfavorable steric interactions between the trisubstituted silicon atom and the adjacent olefin, analogous to results obtained by Schrock and coworkers with vinyltrimethylsilane [8b]. The reaction of Schrock s [W]l catalyst with 

While siloxanes are also amenable to ADMET polymerization, they display trends similar to silanes, in that the steric bulk near the reacting olefin prevents productive metathesis [107]. Specifically, l,l,3,3-tetramethyl-l,3-divinyl-disiloxane proved unreactive, while l,3-diallyl-l,l,3,3-tetramethyldisiloxane almost exclusively cyclized. Still, longer di- and tri-siloxane monomers have been shown to polymerize via ADMET. Ring-chain equilibria are well known for polysiloxanes, and some of these polymers degrade over time via intrachain siloxane exchange reactions to form cyclic oligomers [108]. 

Macrocycles and conjugated polymers have also been obtained by ADMET polymerization of silylene- and siloxane-containing bis-styryl monomers [111]. The silylene linkage led to linear polymers with molecular weights Afjj 2.0 X 10 -6.0 X 10 gmol , whereas the siloxane linkage produced dimeric macrocylces. 

Triblock copolymers of poly(dimethylsiloxane)—polyoctene—poly(dimethyl-siloxane) have also been synthesized by ADMET [112]. The approach involved the initial synthesis of a chlorodimethylsilane-terminated telechehc polyoctenamer (see Section 13.11), which is subsequently reacted with hydroxyl-terminated poly(dimethylsiloxane) (PDMS). 

Silicon compounds containing reactive aryl groups may be chlorosulfonated without loss of the silicon atom by the use of chlorosulfonic acid. Thus, tetraphenoxysilane 451 reacted with excess chlorosulfonic acid at 75-85 C (2j hours) to give the sulfonyl chloride 452. Subsequent reduction of 452 with zinc afforded 4-hydroxyphenylthiol 453 (72% yield, 99.6% purity) this provides an excellent synthetic route to this compound (Equation 140).  

Another example is provided by the sulfonation of benzyltrimethylsilane 454 with chlorosulfonic acid (one equivalent) in chloroform solution to yield the corresponding / -sulfonic acid 455 (Equation 141).  

Siloxanes 456 are cleaved by treatment with chlorosulfonic acid to give the corresponding disilyl sulfates 457 (Equation 142). 

Chlorosulfonic acid reacts with tetramethylsilane 458 to give trimethylsilyl chlorosulfonate 459 (Equation 143).  

Anilinotrimethylsilane 466 reacts with chlorosulfonic acid in 1,2-dichloroethane at low temperature to yield phenylsulfamic acid 467 (Equation 147). 

Information on the oxidation of non-organic silicon compounds is almost totally lacking. Shantarovich measured upper and lower pressure limits for SiH4 02 ignition. With decreasing temperature, the lower pressure limit increased and the upper pressure limit dropped. Emeleus and Stewart studied the effect of vessel diameter and presence of foreign gases on the explosion limits. The results were typical of branched-chain oxidations with wall termination below the lower limit and three-body termination above the upper limit. 

The photodecomposition of SiHCl3 by sunlight for several days in the presence of O2 at 80 °C was studied by Besson and Fournier. HCl was evolved and O2 disappeared. Oxychlorides of silicon were produced, from which (8103)20 was isolated. Action of O3 on SiHQ3 at low temperatures also produced (8103)20 and a viscous liquid containing higher oxychlorides. 

Sharma and Padur reported the occurrence of a chemiluminescent reaction between atomic oxygen and GeH4, but no kinetic data were given. 

Damerell and Emeleus found that arsenic could be oxidized to AS2O3 by N2O above 250 °C. Ignition occurred at 400-450 °C. There was no chemiluminescence and no critical pressure for ignition. 

Madson and Krauskopf found that ASI3 dissolved in benzene decomposed to I2 and AS2O3 in the presence of O2. 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

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All silicon compounds on oxidation yield silica or silicates these are difficult to detect but silica (given by silicates after acid treatment) is insoluble in all acids except hydrofluoric acid. 

Aryl-S02Cl. At present only a few data concerning electrophilic 1,3-substitution with allenic and acetylenic tin or silicon compounds are available. 

Substituted aroyl- and heteroaroyltrimethylsilanes (acylsilanes) are prepared by the coupling of an aroyl chloride with (Me3Si)2 without decarbonylation, and this chemistry is treated in Section 1.2[629], Under certain conditions, aroyl chlorides react with disilanes after decarbonylation. Thus the reaction of aroyl chlorides with disilane via decarbonylation is a good preparative method for aromatic silicon compounds. As an interesting application, trimel-litic anhydride chloride (764) reacts with dichlorotetramethyidisilane to afford 4-chlorodimethylsilylphthalic anhydride (765), which is converted into 766 and used for polymerization[630]. When the reaction is carried out in a non-polar solvent, biphthalic anhydride (767) is formed[631]. Benzylchlorodimethylsilane (768) is obtained by the coupling of benzyl chloride with dichlorotetramethyl-disilane[632,633]. 

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