α-Carbofunctional silanols: synthesis,structure, properties

In the present review, data on methods of synthesis, reactivity, biological activity and structure of α-carbofunctional silanols having X—C—SiOH (X = Hal, O, S, N) geminal moiety, have been classified and analyzed.     

Drug design based on the carbon/silicon switch strategy

Classical bioisosteric substitution is the replacement of a carbon atom by a silicon atom (sila-substitution, carbon/silicon switch). The review is focused on the effects of bioisosteric carbon/silicon switch on the activity of the known pharmaceuticals. In the majority of cases, silicon derivatives show enhanced biological activities and improved pharmacological profiles as compared with the parent carbon drug scaffolds.     

Properties of materials effect of thiokol on properties of epoxy polymers

The complex character of the effect of the concentration of liquid thiokol of brand, I heat treatment, and water on the complex of physicomechanical, relaxation, and adhesion properties of epoxy polymers was demonstrated.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-methyl-<Emphasis Type="Italic">N,N</Emphasis>-bis(silatranylmethyl)amine with trichlorosilane

N,N-Bis(silatranylmethyl)methylamine reacts with trichlorosilane to form the amine hydrochloride and perchloropolysilane, the product of polymerization of dichlorosilylene. In the presence of 1,3-butadiene the main products of the reaction are the amine hydrochloride and 1,1-dichlorosilacyclopentene-3, the product of 1,4-addition of dichlorosilylene to 1,3-butadiene.     

Dehydrochlorination of chloroform by N-methyl-N,N-bis(silatranylmethyl)amine

N,N-Bis(silatranylmethyl)methylamine 1 reacts with chloroform resulting in amine hydrochloride 2 and dichlorocarbene. The formation of the latter was proved by a cyclopropanation reaction and insertion into the Si-H bond. In the presence of cyclohexene, compound 2 and 7,7-dichlorobicyclo[4.1.0]heptane are the major reaction products. Compound 2 and 1-dichloromethylsilatrane were isolated upon the reaction of amine 1 with chloroform and 1-hydrosilantrane.     

PO → Si intramolecular coordination in the derivatives of 1,4‐phosphasilacyclohexane 1‐oxides

The chair and boat conformers for a series of derivatives of 1,4‐phosphasilacyclohexane 1‐oxides have been calculated at the B3LYP/6‐311+G** level of theory in the gas phase and taking into account the effect of solvent polarity using the IEF‐PCM model. The stability of the boat conformers containing pentacoordinate silicon due to formation of the P?O→Si intramolecular coordination bond depends on the environment of the phosphorus atom and polarity of the solvent, and the strength of the transannular bond depends also on the nature of the substituents at the silicon atom. The highly polar boat conformers are strongly stabilized in the DMSO solution. NBO analysis showed the importance of the σ(C? Si) → σ*(H₃C? N) hyperconjugative interaction in the two H₃C? N? C? Si fragments of the ring favoring the formation of the pentacoordinate silicon atom. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

4‐Alkyl‐2,2,6,6‐tetramethyl‐1,4,2,6‐oxaazadisilinanes: synthesis,structure, and conformational analysis

4‐Alkyl‐2,2,6,6‐tetramethyl‐1,4,2,6‐oxaazadisilinanes RN[CH₂Si(Me)₂]₂O [R = Me ( 1 ), i‐Pr ( 2 )] were synthesized by two methods which provided good yields up to 84%. Low temperature NMR study of compounds ( 1 ) and ( 2 ) revealed a frozen ring inversion with the energy barriers of 8.5 and 7.7 kcal/mol at 163 and 143 K, respectively, which is substantially lower than that for their carbon analog, N‐methylmorpholine. DFT calculations performed on the example of molecule ( 1 ) showed that N? Me_ax conformer to exist in the sofa conformation with the coplanar fragment C? Si? O? Si? C, and its N? Me_eq conformer in a flattened chair conformation. Copyright © 2009 John Wiley & Sons, Ltd.     

Precise out-vacuum proton beam monitoring system based on vibrating wire

As an instrument for Korea Multi-purpose Accelerator Complex (KOMAC) facility proton beam profiling, a vibrating wire monitor (VWM) has been installed and tested at TR23 target room. Experiments were done at very low (100 nA) beam current conditions. At the number of particles about 10¹¹ proton/train and trains repetition rate of 0.1 Hz we have measured the beam profile by a few scanning steps. The experience accumulated in these experiments turned out to be useful for the VWM upgrades (e. g. understanding interactions of protons with wire materials and heat transfer processes) and will be particularly helpful for the KOMAC beam halo measurements in the future high-current operation.     

A new method for the preparation of 1-(chloromethyl)- and 1-(dichloromethyl)silatranes

A preparative method for the synthesis of 1-(chloromethyl)- and 1-(dichloromethyl)silatranes was developed based on the reactions of 1-chlorosilatrane with the binary P(NMe₂)₃–СHX₃ system (X₃ = HBrCl, Cl₃).

     

Features of rheological and electrophysical properties of compositions based on polyvinyl alcohol and carboxymethylcellulose

A study has been made of the rheological and electrophysical properties (conductivity and dielectric loss angle) of aqueous solutions of polyvinyl alcohol (PVA), water-soluble carboxymethylcelluloses (Na-CMC), and compositions based on PVA and Na-CMC or methylcellulose, with PVA solution concentration 1% to 10% by weight and cellulose ether content in the polymer mixture up to 50% by weight. It was found that anisotropic structures can be formed in solutions based on PVA compositions under the influence of an orienting mechanical field; this is related to the formation of structure-sensitive associates in solution in the form of complexes.Paper presented at the 9th International Conference on the Mechanics of Composite Materials, Riga, October 1995.Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 6, pp. 742–753, November–December, 1995.