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Thioselenide
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 all ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenide Sulfide
In chemistry, a selenosulfide refers to distinct classes of inorganic compound, 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disulfide
In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In biology, disulfide bridges formed between thiol groups in two cysteine residues are an important component of the secondary and tertiary structure of proteins. ''Persulfide'' usually refers to compounds. In inorganic chemistry disulfide usually refers to the corresponding anion (−S−S−). Organic disulfides Symmetrical disulfides are compounds of the formula . Most disulfides encountered in organo sulfur chemistry are symmetrical disulfides. Unsymmetrical disulfides (also called heterodisulfides) are compounds of the formula . They are less common in organic chemistry, but most disulfides in nature are unsymmetrical. Properties The disulfide bonds are strong, with a typical bond dissociation energy of 60 kcal/mol (251&nbs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimethyl Thioselenide
Ethane ( , ) is an Organic compound, organic chemical compound with chemical formula . At Standard conditions for temperature and pressure, standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is List of purification methods in chemistry, isolated on an industrial scale from natural gas and as a petrochemical by-product of oil refinery, petroleum refining. Its chief use is as feedstock for ethylene production. Related compounds may be formed by replacing a hydrogen atom with another functional group; the ethane moiety (chemistry), moiety is called an ethyl group. For example, an ethyl group linked to a hydroxyl group yields ethanol, the alcohol in beverages. History Ethane was first synthesised in 1834 by Michael Faraday, applying electrolysis of a potassium acetate solution. He mistook the hydrocarbon product of this reaction for methane and did not investigate it further. During the period 1847–1849, in an effort to vind ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allium
''Allium'' is a genus of monocotyledonous flowering plants that includes hundreds of species, including the cultivated onion, garlic, scallion, shallot, leek, and chives. The generic name ''Allium'' is the Latin word for garlic,Gledhill, David (2008). "The Names of Plants". Cambridge University Press. (hardback), (paperback). pp 43 and the type species for the genus is '' Allium sativum'' which means "cultivated garlic".''Allium'' In: Index Nominum Genericorum. In: Regnum Vegetabile (see ''External links'' below). Carl Linnaeus first described the genus ''Allium'' in 1753. Some sources refer to Greek ἀλέω (aleo, to avoid) by reason of the smell of garlic. Various ''Allium'' have been cultivated from the earliest times, and about a dozen species are economically important as crops, or garden vegetables, and an increasing number of species are important as ornamental plants. The decision to include a species in the genus ''Allium'' is taxonomically difficult, and spec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semiconductor Materials
A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways by introducing impurities (" doping") into the crystal structure. When two differently doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers, which include electrons, ions, and electron holes, at these junctions is the basis of diodes, transistors, and most modern electronics. Some examples of semiconductors are silicon, germanium, gallium arsenide, and elements near the so-called "metalloid staircase" on the periodic table. After silicon, gallium arsenide is the second-most common semiconductor and is used in laser diodes, solar cells, microwave-frequency integrated circuits, and others. Silicon is a critical element for fabricat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenides
A selenide is a chemical compound containing a selenium anion with oxidation number of −2 (Se2−), much as sulfur does in a sulfide. The chemistry of the selenides and sulfides is similar. Similar to sulfide, in aqueous solution, the selenide ion, Se2−, is prevalent only in very basic conditions. In neutral conditions, hydrogen selenide ion, HSe−, is most common. In acid conditions, hydrogen selenide, H2Se, is formed. Some selenides are reactive to oxidation by air. Owing to the greater reducing power of selenide, metal selenides are more easily decomposed to the elements than are sulfides (tellurides are even more labile). Selenides of electropositive metals: such as aluminium selenide readily hydrolyse, even in moist air, evolving toxic hydrogen selenide gas. Pure selenide minerals are rare, instead selenium tends to partially substitute for sulfide in many sulfide minerals. The degree of substitution is only of commercial interest for copper sulfide ores, in which case ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cadmium Compounds
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of its compounds, and like mercury, it has a lower melting point than the transition metals in groups 3 through 11. Cadmium and its congeners in group 12 are often not considered transition metals, in that they do not have partly filled ''d'' or ''f'' electron shells in the elemental or common oxidation states. The average concentration of cadmium in Earth's crust is between 0.1 and 0.5 parts per million (ppm). It was discovered in 1817 simultaneously by Stromeyer and Hermann, both in Germany, as an impurity in zinc carbonate. Cadmium occurs as a minor component in most zinc ores and is a byproduct of zinc production. Cadmium was used for a long time as a corrosion-resistant plating on steel, and cadmium compounds are used as red, orange ... [...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 earth s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organosulfur Compounds
Organosulfur compounds are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g., saccharin. Nature abounds with organosulfur compounds—sulfur is vital for life. Of the 20 common amino acids, two (cysteine and methionine) are organosulfur compounds, and the antibiotics penicillin and sulfa drugs both contain sulfur. While sulfur-containing antibiotics save many lives, sulfur mustard is a deadly chemical warfare agent. Fossil fuels, coal, petroleum, and natural gas, which are derived from ancient organisms, necessarily contain organosulfur compounds, Desulfurization, the removal of which is a Claus process, major focus of oil refineries. Sulfur shares the chalcogen group with oxygen, selenium, and tellurium, and it is expected that organosulfur compounds have similarities with carbon–oxygen, carbon–selenium, and carbon–tellurium compounds. A classical chemical test for the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organoselenium Compounds
Organoselenium compounds (or seleno-organic) are chemical compounds containing carbon-to-selenium chemical bonds. Organoselenium chemistry is the corresponding science exploring their properties and reactivity. Selenium belongs with oxygen and sulfur to the group 16 elements or chalcogens, and similarities in chemistry are to be expected. Organoselenium compounds are found at trace levels in ambient waters, soils and sediments. Selenium can exist with oxidation state −2, +2, +4, +6. Se(II) is the dominant form in organoselenium chemistry. Down the group 16 column, the bond strength becomes increasingly weaker (234 kilojoule, kJ/mole (unit), mol for the C−Se bond and 272 kJ/mol for the C−S bond) and the bond lengths longer (C−Se 198 pm, C−S 181 pm and C−O 141 pm). Selenium compounds are more nucleophilic than the corresponding sulfur compounds and also more acidic. The pKa, p''K''a values of XH2 are 16 for oxygen, 7 for sulfur and 3.8 for selenium. In contrast to sulfoxi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cadmium Selenide
Cadmium selenide is an inorganic compound with the formula Cadmium, CdSelenide, Se. It is a black to red-black solid that is classified as a II-VI semiconductor of the n-type semiconductor, n-type. Much of the current research on this compound is focused on its nanoparticles. Structure Three crystalline forms of CdSe are known which follow the structures of: Wurtzite (crystal structure), wurtzite (hexagonal), Cubic crystal system#Zincblende structure, sphalerite (cubic) and Cubic crystal system#Rock-salt structure, rock-salt (cubic). The sphalerite CdSe structure is unstable and converts to the wurtzite form upon moderate heating. The transition starts at about 130 °C, and at 700 °C it completes within a day. The rock-salt structure is only observed under high pressure. Production The production of cadmium selenide has been carried out in two different ways. The preparation of bulk crystalline CdSe is done by the High-Pressure Vertical Bridgman method or High-Pressur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cadmium Sulfide
Cadmium sulfide is the inorganic compound with the formula CdS. Cadmium sulfide is a yellow solid.Egon Wiberg, Arnold Frederick Holleman (2001''Inorganic Chemistry'' Elsevier It occurs in nature with two different crystal structures as the rare minerals greenockite and hawleyite, but is more prevalent as an impurity substituent in the similarly structured zinc ores sphalerite and wurtzite, which are the major economic sources of cadmium. As a compound that is easy to isolate and purify, it is the principal source of cadmium for all commercial applications. Its vivid yellow color led to its adoption as a pigment for the yellow paint "cadmium yellow" in the 18th century. Production Cadmium sulfide can be prepared by the precipitation from soluble cadmium(II) salts with sulfide ion. This reaction has been used for gravimetric analysis and qualitative inorganic analysis.The preparative route and the subsequent treatment of the product, affects the polymorphic form that is produced ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
