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Selenide Bromide
A selenide is a chemical compound containing a selenium with oxidation number of −2. Similar to sulfide, selenides occur both as inorganic compounds and as organic derivatives, which are called organoselenium compound. Inorganic selenides The parent inorganic selenide is hydrogen selenide (H2Se). It is a colorless, malodorous, toxic gas. It dissolves in aqueous solution, to give the hydrogenselenide or biselenide ion HSe−. At higher pH, selenide forms. Solutions of hydrogen selenide and selenide are oxidized by air to give elemental selenium: : Most elements form selenides. They sometimes have salt-like properties, e.g. sodium selenide, but most exhibit covalent bonding, e.g. molybdenum diselenide. Their properties are diverse, mirroring the diverse properties of the corresponding sulfides. As indicated by the fact that only a few thousand tons of selenium are produced annually, the subset of selenium compounds called selenides find few applications. Commercially signif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenium
Selenium is a chemical element; it has symbol (chemistry), symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elemental state or as pure ore compounds in Earth's crust. Selenium ( ) was discovered in 1817 by , who noted the similarity of the new element to the previously discovered tellurium (named for the Earth). Selenium is found in :Sulfide minerals, metal sulfide ores, where it substitutes for sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores. Minerals that are pure selenide or selenate compounds are rare. The chief commercial uses for selenium today are glassmaking and pigments. Selenium is a semiconductor and is used in photocells. Applications in electronics, once important, have been mostly replaced with silicon semiconductor devices. Selenium is still used in a few types of Direct current, DC power surge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Substitution (chemistry)
A substitution reaction (also known as single displacement reaction or single substitution reaction) is a chemical reaction during which one functional group in a chemical compound is replaced by another functional group. Substitution reactions are of prime importance in organic chemistry. Substitution reactions in organic chemistry are classified either as electrophilic or nucleophilic depending upon the reagent involved, whether a reactive intermediate involved in the reaction is a carbocation, a carbanion or a free radical, and whether the substrate is aliphatic or aromatic. Detailed understanding of a reaction type helps to predict the product outcome in a reaction. It also is helpful for optimizing a reaction with regard to variables such as temperature and choice of solvent. A good example of a substitution reaction is halogenation. When chlorine gas (Cl2) is irradiated, some of the molecules are split into two chlorine radicals (Cl•), whose free electrons are strongly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chalcogenides
: 220px, Cadmium sulfide, a prototypical metal chalcogenide, is used as a yellow pigment. A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elements of the periodic table are defined as chalcogens, the term chalcogenide is more commonly reserved for sulfides, selenides, tellurides, and polonides, rather than oxides. Many metal ores exist as chalcogenides. Photoconductive chalcogenide glasses are used in xerography. Some pigments and catalysts are also based on chalcogenides. The metal dichalcogenide MoS2 is a common solid lubricant. Alkali metal and alkaline earth chalcogenides Alkali metal and alkaline earth monochalcogenides are salt-like, being colourless and often water-soluble. The sulfides tend to undergo hydrolysis to form derivatives containing bisulfide (SH−) anions. The alkali metal chalcogenides often crystallize with the antifluorite structure and the alkaline eart ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenides
A selenide is a chemical compound containing a selenium with oxidation number of −2. Similar to sulfide, selenides occur both as inorganic compounds and as organic derivatives, which are called organoselenium compound. Inorganic selenides The parent inorganic selenide is hydrogen selenide (H2Se). It is a colorless, malodorous, toxic gas. It dissolves in aqueous solution, to give the hydrogenselenide or biselenide ion HSe−. At higher pH, selenide forms. Solutions of hydrogen selenide and selenide are oxidized by air to give elemental selenium: : Most elements form selenides. They sometimes have salt-like properties, e.g. sodium selenide, but most exhibit covalent bonding, e.g. molybdenum diselenide. Their properties are diverse, mirroring the diverse properties of the corresponding sulfides. As indicated by the fact that only a few thousand tons of selenium are produced annually, the subset of selenium compounds called selenides find few applications. Commercially s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfoselenide
In chemistry, a selenosulfide refers to distinct classes of inorganic and organic compounds containing sulfur and selenium. The organic derivatives contain Se-S bonds, whereas the inorganic derivatives are more variable. Organic selenosulfides These species are classified as both organosulfur and organoselenium compounds. They are hybrids of organic disulfides and organic diselenides. Preparation, structure, and reactivity Selenosulfides have been prepared by the reaction of selenyl halides with thiols: : The equilibrium between diselenides and disulfides lies on the left: :RSeSeR + R'SSR' 2 RSeSR' Because of the facility of this equilibrium, many of the best characterized examples of selenosulfides are cyclic, whereby S-Se bonds are stabilized intramolecularly. One example is the 1,8-selenosulfide of naphthalene. The selenium-sulfur bond length is about 220 picometers, the average of a typical S-S and Se-Se bond. Occurrence Selenosulfide groups can be found in almost a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Copper Selenide
Copper selenide may refer to: * Copper(I) selenide * Copper(II) selenide Selenides Copper compounds {{Short pages monitor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lead Selenide
Lead selenide (PbSe), or lead(II) selenide, a selenide of lead, is a semiconductor material. It forms cubic crystals of the NaCl structure; it has a direct bandgap of 0.27 eV at room temperature. (Note that incorrectly identifies PbSe and other IV–VI semiconductors as indirect gap materials.) A grey solid, it is used for manufacture of infrared detectors for thermal imaging. The mineral clausthalite is a naturally occurring lead selenide. It may be formed by direct reaction between its constituent elements, lead and selenium. Infrared detection PbSe was one of the first materials found to be sensitive to the infrared radiation used for military applications. Early research works on the material as infrared detector were carried out during the 1930s and the first useful devices were processed by Germans, Americans and British during and just after World War II. Since then, PbSe has been commonly used as an infrared photodetector in multiple applications, from spectro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indium(III) Selenide
Indium(III) selenide is a compound of indium and selenium. It has potential for use in photovoltaic devices and has been the subject of extensive research. The two most common phases, α and β, have a layered structure, while γ has a "defect wurtzite structure." In all, five polymorphs are known: α, β, γ, δ, κ. The α-β phase transition is accompanied by a change in electrical conductivity. The band gap of γ-In2Se3 is approximately 1.9 eV. Preparation The method of production influences the polymorph generated. For example, thin films of pure γ-In2Se3 have been produced from trimethylindium (InMe3) and hydrogen selenide via MOCVD techniques. : A conventional route entails heating the elements in a sealed tube: : See also * Gallium(III) selenide * Indium chalcogenides *Nanoparticle A nanoparticle or ultrafine particle is a particle of matter 1 to 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gallium(II) Selenide
Gallium(II) selenide ( Ga Se) is a chemical compound. It has a hexagonal layer structure, similar to that of GaS. It is a photoconductor, a second harmonic generation crystal in nonlinear optics, and has been used as a far-infrared conversion material at 14–31 THz and above. Uses It is said to have potential for optical applications but the exploitation of this potential has been limited by the ability to readily grow single crystals Gallium selenide crystals show great promise as a nonlinear optical material and as a photoconductor. Non-linear optical materials are used in the frequency conversion of laser light. Frequency conversion involves the shifting of the wavelength of a monochromatic source of light, usually laser light, to a higher or lower wavelength of light that cannot be produced from a conventional laser source. Several methods of frequency conversion using non-linear optical materials exist. Second harmonic generation leads to doubling of the frequency of in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Se-methylselenocysteine
Methylselenocysteine (Me-Sec), also known as ''Se''-methylselenocysteine (SeMSC), is an analog of ''S''-methylcysteine in which the sulfur atom is replaced with a selenium atom. Occurrence Methylselenocysteine is found in many vegetables: "as much as 80% of the total selenium" found in ''Allium'' species (onion, leek, garlic, ramps) ''Brassica'' species (broccoli, radish, Brussels sprouts, cabbage), and milk vetch (''Astragalus'' species, Fabaceae) is present as ''Se''-methylselenocysteine. It is also present in selenized yeast (''Saccharomyces cerevisiae'' grown in a high-selenium culture). Biosynthesis In plants it is produced by a dedicated selenocysteine methyltransferase. Adding inorganic selenium to the soil increases the expression of the gene in plants. In yeast it is also made by a selenomethyltransferase, though as no specific enzyme has been identified, it is possible that this happens via a promiscuous reaction of another enzyme. Function Me-Sec activates a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenomethionine
Selenomethionine (SeMet) is a naturally occurring amino acid. The L-selenomethionine enantiomer is the main form of selenium found in Brazil nuts, cereal grains, soybeans, and grassland legumes, while ''Se''-methylselenocysteine, or its γ-glutamyl derivative, is the major form of selenium found in ''Astragalus'', ''Allium'', and ''Brassica'' species. ''In vivo'', selenomethionine is randomly incorporated instead of methionine. Selenomethionine is readily oxidized. Selenomethionine's antioxidant activity arises from its ability to deplete reactive oxygen species. Selenium and methionine also play separate roles in the formation and recycling of glutathione, a key endogenous antioxidant in many organisms, including humans. In proteins Selenium and sulfur are chalcogens that share many chemical properties so the substitution of methionine with selenomethionine may have only a limited effect on protein structure and function. Indeed, bacteria can tolerate a very high amount of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimethyl Selenide
Dimethyl selenide is the organoselenium compound with the formula (CH3)2Se. This colorless, malodorous liquid is the simplest selenoether. It occurs in trace amounts in anaerobic environments and in the atmosphere due to biomethylation of selenium. Dimethyl selenide is prepared by treating Se2− sources with electrophilic methylating agents such as methyl iodide: :Na2Se + 2 CH3I → (CH3)2Se + 2 NaI The carbon–selenium bond length is 1.943 Å and the C–Se–C bond angle is 96.2°, as determined by rotational microwave spectroscopy. Similar dimensions of 1.98 Å and 98° are found by gas electron diffraction Gas electron diffraction (GED) is one of the applications of electron diffraction techniques. The target of this method is the determination of the structure of gaseous molecules, i.e., the geometrical arrangement of the atoms from which a molec .... References {{Selenium compounds Selenium(−II) compounds Selenoethers Foul-smelling chemicals Methyl compou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
