- M-SG reducing agent
In M-SG an
alkali metal is absorbed intosilica gel at elevated temperatures. The resulting black powder material is an effectivereducing agent and safe to handle as opposed to the pure metal. The material can also be used as adesiccant and as ahydrogen source ["Alkali Metals Plus Silica Gel: Powerful Reducing Agents and Convenient Hydrogen Sources " James L. Dye, Kevin D. Cram, Stephanie A. Urbin, Mikhail Y. Redko, James E. Jackson, and Michael LefenfeldJ. Am. Chem. Soc. , 127 (26), 9338 -9339, 2005 [http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/2005/127/i26/abs/ja051786+.html Abstract] ] .The metal is either
sodium or a sodium -potassium alloy (Na2K). The molten metal is mixed with silica gel under constant agitation atroom temperature . This phase 0 material must be handled in an inert atmosphere. Heating phase 0 at 150°C takes it to phase I. When this material is exposed to dry oxygen the reducing power is not affected. At further heating to 400°C phase II can be handled safely in an ambient environment.The metal reacts with the silicon gel in an
exothermic reaction in which Na4Si4 nanoparticles are formed. The powder reacts with water to formhydrogen .Compounds such as
biphenyl andnaphthalene are reduced by the powder and form highly coloured radical anions. The powder can also be introduced in acolumn chromatography setup and eluted with organic reactants in order to probe the reducing power. The powder is mixed with additional (wet) silica gel which provides additional hydrogen. ABirch reduction of naphthalene takes 5 minuteselution time . The column converts benzyl chloride tobibenzyl in aWurtz coupling and in a similar fashion dibenzothiophene is reduced tobiphenyl .See also
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Potassium graphite References
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