Di-methyl silicones and siloxanes

CLASS Polysiloxanes di-methyl silicones and siloxanes STRUCTURE -[(CH3)2Si-0-] ... 

See Phenylmethyl polysiloxane Siloxanes and silicones, dimethyl, [(12-hydroxy-1-oxooctadecyl) oxy]-terminated. See Dimethiconol hydroxystearate Siloxanes and silicones, dimethyl, 3-hydroxypropyl methyl-, ethers with PEG dihydrogen phosphate, compds. with N,N -bis [3-(di methyl ami no) propyl]-C18-unsaturated amide dimers. See Dilinoleamidopropyl dimethylamine dimethicone copolyol phosphate,... 

Unfortunately, the reaction fails with most a,o>-dienes. One reason for this is that the Ru catalyst isomerizes terminal a,co-dienes such as 1,7-heptadiene to internal dienes which are not reactive. Conjugated dienes such as 1,3-butadiene or 2,3-di-methyl-1,3-butadiene are also unreactive. Further C-C double bonds substituted with electron withdrawing groups such those of methyl acrylate, acrylonitrile, or methyl vinyl ketones do not react. So why are the C-C double bonds of vinylsilanes, vinyl-siloxanes and styrenes reactive Perhaps the simplest explanation is that silicon and... 

This sensitivity toward lateral attacks explains the four times shorter duration of action of sila-meprobamate compared to its carbon isostere on a model of tranquiUizing activity in mice (rotarod test, potentiation of hexobarbital-induced sleep, and intraperitoneal injection). " On the other hand, when given orally, sila-meprobamate is practically inactive. One of the first metabolites formed has been characterized as being a di-siloxane (Figure 15.67). For the two phenyl-trimethylsilyl-derived AChE inhibitors, the rather positively charged trimethyl-silyl group mimics the trimethyl-ammonium function present in acetylcholine. Eor these compound metabolic oxidation does not take place on the silicon, but on one of methyl groups (S1-CH3 Si—CH2—OH). ... 

The industrial manufacture of siloxanes has its beginnings with pure silicon, which is pulverized and allowed to react with methyl chloride in a pressurized fluid bed reactor in the presence of a copper catalyst. Under carefully controlled conditions, this reaction yields a mixture of methylchlorosilanes in which di-methyIdichlorosilane predominates ... 

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