1,1,1,3,3,3-六甲基二硅氮烷与PhMe_3N^+Br_3~–选择性催化醇与酚的三甲基硅烷化反应(英文)

An efficient procedure for the trimethylsilylation of alcohols and phenols is presented.The combination of 1,1,1,3,3,3-hexamethyldisilazane and a catalytic amount of phenyltrimethylammonium tribromide(PhMe3N+Br3?) was found to be effective for the trimethylsilylation of alcohols and phenols.The protection reaction is very simple and homogenously performed in dichloromethane at room temperature and mild conditions.

可重复使用的丙磺酸功能化纳米结构SBA-15上醇和酚与六甲基二硅氮烷的硅烷化反应(英文)

Various alcohols and phenols were trimethylsilylated in excellent yields using hexamethyldisilazane in the presence of catalytic amounts of environmentally friendly, hydrophobic, highly thermal stable, and completely heterogeneous sulfonic acid functionalized mesostructured SBA-15 in dichloromethane at ambient temperature. Primary, bulky secondary, tertiary, and phenolic hydroxyl functional groups were transformed to the corresponding trimethylsilyl ethers in excellent yields. The simple experimental procedure was accompanied by easy recovery and the catalyst was reusable (at least 18 reaction cycles); these are attractive features of this protocol.

Dispersion hydrophobic electrolyte enables lithium-oxygen battery enduring saturated water vapor

Li-O_(2) batteries gain widespread attention as a can didate for next-generati on energy storage devices due to their extraordinary theoretic specific energy.The semi-open structure of Li-O_(2) batteries causes many parasitic reactions,especially related to water.Water is a double-edged sword,which destroys Li anode and simultaneously triggers a solution-based pathway of the discharge product.In this work,hexamethyldisilazane(HMDS)is introduced into the electrolyte of an aprotic Li-O_(2) battery.HMDS has a strong ability to combine with a trace of water to gen erate a hydrophobic hexamethyldisiloxa ne(MM),which eliminates water from the electrolyte decomposition and then prevents the Li anode from producing the insulating LiOH with water.In this case,the hydrophobic MM disperses in the ether-based electrolyte,forming a dispersion hydrophobic electrolyte.This electrolyte can anchor water from the environment on the cathode side,which triggers a solution-based pathway and regulates the growth morphology of the discharge product and consequently increases the discharge capacity.Compared with the Li-O_(2) battery without the HMDS,the HMDS-containing Li-O_(2) battery contributes an about 13-fold increase of cyclability(400 cycles,1800 h)in the extreme environment of saturated water vapor.This work opens a new approach for directly operating aprotic Li-O_(2) batteries in ambient air.

Combustion Synthesis of SiO_2 on the Aluminum Plate

The approach of utilizing combustion synthesis to make fine particles of SiO2, A12O3 and TiO2 is a quite modern technology. Through the chemical reaction in post-flame region, fine SiO2 particles can be formed with high purity on plate surface. Therefore, the combustion synthesis of SiO2 powders is an important area for further research and development especially for the application of SiO2 in the semiconductor industry. This investigation proposes an experimental approach （i.e., a gas-phase combustion synthesis） using two different kinds of organic compounds, Hexamethyldisilazane （HMDSA） and Hexamethyldisioxane （HMDSO）, as the silicon precursors. A premixed gas burner is chosen with C3H8 as fuel air as oxidant and part of the air was used as the carrying gas to entrain HMDSA/HMDSO vapor into the combustible mixture. Observations show that the C3H8/air flame changed color from a pale-blue flame to light yellow and then orange when different amounts of precursors were introduced. Through the chemical reaction in the post-flame region, fine SiO2 particles were formed in the gas phase and then quenched and collectal on an aluminum flat plate. The objective of this paper is to study the effects of HMDSO and HMDSA concentrations and flame temperatures on the synthesis of SiO2 particles.