M-SG reducing agent
Encyclopedia
In M-SG an alkali metal
is absorbed into silica gel
at elevated temperatures. The resulting black powder material is an effective reducing agent
and safe to handle as opposed to the pure metal. The material can also be used as a desiccant
and as a hydrogen
source .
The metal is either sodium
or a sodium - potassium
alloy
(Na2K
). The molten metal is mixed with silica gel under constant agitation at room temperature
. This phase 0 material must be handled in an inert atmosphere. Heating phase 0 at 150 °C (302 °F) 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 (752 °F) 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 form hydrogen
.
Compounds such as biphenyl
and naphthalene
are reduced by the powder and form highly coloured radical anion
s. The powder can also be introduced in a column 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. A Birch reduction
of naphthalene takes 5 minutes elution time. The column converts benzyl chloride to bibenzyl
in a Wurtz coupling and in a similar fashion dibenzothiophene is reduced to biphenyl
.
Alkali metal
The alkali metals are a series of chemical elements in the periodic table. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, along with hydrogen. The alkali metals are lithium , sodium , potassium , rubidium , caesium , and francium...
is absorbed into silica gel
Silica gel
Silica gel is a granular, vitreous, porous form of silica made synthetically from sodium silicate. Despite its name, silica gel is a solid. It is a naturally occurring mineral that is purified and processed into either granular or beaded form...
at elevated temperatures. The resulting black powder material is an effective reducing agent
Reducing agent
A reducing agent is the element or compound in a reduction-oxidation reaction that donates an electron to another species; however, since the reducer loses an electron we say it is "oxidized"...
and safe to handle as opposed to the pure metal. The material can also be used as a desiccant
Desiccant
A desiccant is a hygroscopic substance that induces or sustains a state of dryness in its local vicinity in a moderately well-sealed container....
and as a hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
source .
The metal is either sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
or a sodium - potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
(Na2K
NaK
NaK, or sodium-potassium alloy, an alloy, of potassium , and sodium , is usually liquid at room temperature. Various commercial grades are available. NaK is highly reactive with water and may catch fire when exposed to air, so must be handled with special precautions...
). The molten metal is mixed with silica gel under constant agitation at room temperature
Room temperature
-Comfort levels:The American Society of Heating, Refrigerating and Air-Conditioning Engineers has listings for suggested temperatures and air flow rates in different types of buildings and different environmental circumstances. For example, a single office in a building has an occupancy ratio per...
. This phase 0 material must be handled in an inert atmosphere. Heating phase 0 at 150 °C (302 °F) 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 (752 °F) phase II can be handled safely in an ambient environment.
The metal reacts with the silicon gel in an exothermic reaction
Exothermic reaction
An exothermic reaction is a chemical reaction that releases energy in the form of light or heat. It is the opposite of an endothermic reaction. Expressed in a chemical equation:-Overview:...
in which Na4Si4 nanoparticles
Nanotechnology
Nanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally, nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension sized from 1 to 100 nanometres...
are formed. The powder reacts with water to form hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
.
Compounds such as biphenyl
Biphenyl
Biphenyl is an organic compound that forms colorless crystals. It has a distinctively pleasant smell. Biphenyl is an aromatic hydrocarbon with a molecular formula 2...
and naphthalene
Naphthalene
Naphthalene is an organic compound with formula . It is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromatic hydrocarbon, naphthalene's structure consists of a fused pair of benzene rings...
are reduced by the powder and form highly coloured radical anion
Radical ion
A radical ion is a free radical species that carries a charge. Radical ions are encountered in organic chemistry as reactive intermediates and in mass spectrometry as gas phase ions...
s. The powder can also be introduced in a column chromatography
Column chromatography
Column chromatography in chemistry is a method used to purify individual chemical compounds from mixtures of compounds. It is often used for preparative applications on scales from micrograms up to kilograms.The main advantage of column chromatography is the relatively low cost and disposability...
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. A Birch reduction
Birch reduction
The Birch Reduction is an organic reaction which is particularly useful in synthetic organic chemistry. The reaction was reported in 1944 by the Australian chemist Arthur Birch working in the Dyson Perrins Laboratory in the University of Oxford, building on earlier work by Wooster and Godfrey in...
of naphthalene takes 5 minutes elution time. The column converts benzyl chloride to bibenzyl
Bibenzyl
Bibenzyl is an aromatic chemical compound that can be considered a derivative of ethane in which one phenyl group is attached to each carbon atom....
in a Wurtz coupling and in a similar fashion dibenzothiophene is reduced to biphenyl
Biphenyl
Biphenyl is an organic compound that forms colorless crystals. It has a distinctively pleasant smell. Biphenyl is an aromatic hydrocarbon with a molecular formula 2...
.