Siloxane ring compounds

Viscosities of the siloxanes were predicted over a temperature range of 298-348 K. The semi-log plot of viscosity as a function of temperature was linear for the ring compounds. However, for the chain compounds, the viscosity increased rapidly with an increase in the chain length of the molecule. A simple 2-4-1 neural network architecture was used for the viscosity predictions. The molecular configuration was not considered here because of the direct positive effect of addition of both M and D groups on viscosity. The two input variables, therefore, were the siloxane type and the temperature level. Only one hidden layer with four nodes was used. The predicted variable was the viscosity of the siloxane. 

Oxidation by Oxygen, Perbenzoic Acid, and Other Substances Acyclic peralkylated polysilanes are sufficiently stable to air oxidation to be handled at moderate to relatively high temperature without specific precautions. On the other hand, five-membered ring compounds are easily attacked by molecular oxygen and converted to siloxanes 21, 115, 122). 

Silylmethyl radical cyclizations are a related class of reactions in which the heterocycle serves a temporary purpose to direct the introduction of a methyl or hydroxymethyl group adjacent to the hydroxy group. Starting from the optically active allylic decalin alcohol, reaction with bromomethyl(chloro)dimethylsilane gives the a-bromosilyl ether. Treatment with tributyltin hydride affords the stereoselective cyclization to a five-membered siloxane62. The siloxane ring is converted either to the a.r-dihydroxy compound, or to the ot-methylated derivative63. 

With a related class of compounds, the phenylated cyclosiloxanes, the effect of siloxane ring size on the spectral characteristics of the blue photoluminescence was investigated in more detail. It was shown that the cyclosiloxane symmetry is the controlling parameter for the spectral distribution of the phosphorescence intensity as... 

Si-0 Stretching Frequencies of Siloxane Rings in Model Compounds and u-SiOj. 

One of the recent advances in the chemistry of organosilicon compounds is the synthesis of cyclolinear polyorganosiloxanes (CLPOS) [83,84], whose linear macromolecules are consdncted from siloxane rings of different size which are repeated tens and hundreds of times and are joined by oxygen atoms ... 

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