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Salt-free Reduction
In chemistry, salt-free reduction describes methodology for reduction of metal halides by electron-rich trimethylsilyl reagents. Traditional reductions of metal halides are accomplished with alkali metals, a process that cogenerates alkali metal salts. Using the salt-free reduction, the reduction of metal halides is accompanied by formation of neutral organic compounds that can be easily removed from the inorganic or organometallic product. In addition to the reduction of metal halides, the reagents associated with this methodology are applicable to deoxygenation of organic substrates. A typical reducing agent is N,N'-bis(trimethylsilyl)-4,4'-bipyridinylidene. Related pyrazine- and cyclohexadiene-based reagents have been developed. They are red or orange THF-soluble solids. The bipyridine reagent is produced by reduction of 4,4'-bipyridine in the presence of trimethylsilyl chloride Trimethylsilyl chloride, also known as chlorotrimethylsilane is an organosilicon compound (silyl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a Chemical reaction, reaction with other Chemical substance, substances. Chemistry also addresses the nature of chemical bonds in chemical compounds. In the scope of its subject, chemistry occupies an intermediate position between physics and biology. It is sometimes called the central science because it provides a foundation for understanding both Basic research, basic and Applied science, applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant growth (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the properties ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metal Halide
Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. A few metal halides are discrete molecules, such as uranium hexafluoride, but most adopt polymeric structures, such as palladium chloride. File:NaCl polyhedra.png, Sodium chloride crystal structure File:Uranium-hexafluoride-unit-cell-3D-balls.png, Discrete UF6 molecules File:Alpha-palladium(II)-chloride-xtal-3D-balls.png, Infinite chains of one form of palladium chloride Preparation The halogens can all react with metals to form metal halides according to the following equation: :2M + nX2 → 2MXn where M is the metal, X is the halogen, and MXn is the metal halide. In practice, this type of reaction may be very exothermic, hence impractical as a preparative technique. Additionally, many transition metals can adopt multiple oxidation states, which complicates matters. As the halogens are strong oxidizers, direct combination of the elements us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron-rich
In chemistry, electron-rich is jargon that is used in multiple related meanings with either or both kinetic and thermodynamic implications: *with regards to electron-transfer, electron-rich species have low ionization energy and/or are reducing agents. Tetrakis(dimethylamino)ethylene is an electron-rich alkene because, unlike ethylene, it forms isolable radical cation. In contrast, electron-poor alkene tetracyanoethylene is an electron acceptor, forming isolable anions. *with regards to acid-base reactions, electron-rich species have high pKa's and react with weak Lewis acids. *with regards to nucleophilic substitution reactions, electron-rich species are relatively strong nucleophiles, as judged by rates of attack by electrophiles. For example, compared to benzene, pyrrole is more rapidly attacked by electrophiles. Pyrrole is therefore considered to be an electron-rich aromatic ring. Similarly, benzene derivatives with electron-donating groups (EDGs) are attacked by electr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deoxygenation
Deoxygenation is a chemical reaction involving the removal of oxygen atoms from a molecule. The term also refers to the removal of molecular oxygen (O2) from gases and solvents, a step in air-free technique and gas purifiers. As applied to organic compounds, deoxygenation is a component of fuels production as well a type of reaction employed in organic synthesis, e.g. of pharmaceuticals. Deoxygenation of C-O bonds With replacement by H2 The main examples involving the replacement of an oxo group by two hydrogen atoms (A=O → AH2) are hydrogenolysis. Typical examples use metal catalysts and H2 as the reagent. Conditions are typically more forcing than hydrogenation. Stoichiometric reactions that effect deoxygenation include the Wolff–Kishner reduction for aryl ketones. The replacement of a hydroxyl group by hydrogen (A-OH → A-H) is the point of the Barton–McCombie deoxygenation and the Markó–Lam deoxygenation. Biomass valorization Deoxygenation is an important ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrazine
Pyrazine is a heterocyclic aromatic organic compound with the chemical formula C4H4N2. It is a symmetrical molecule with point group D2h. Pyrazine is less basic than pyridine, pyridazine and pyrimidine. It is a ''"deliquescent crystal or wax-like solid with a pungent, sweet, corn-like, nutty odour"''. Pyrazine and a variety of alkylpyrazines are flavor and aroma compounds found in baked and roasted goods. Tetramethylpyrazine (also known as ligustrazine) is reported to scavenge superoxide anion and decrease nitric oxide production in human Granulocytes. Synthesis Many methods exist for the organic synthesis of pyrazine and its derivatives. Some of these are among the oldest synthesis reactions still in use. In the Staedel–Rugheimer pyrazine synthesis (1876), 2-chloroacetophenone is reacted with ammonia to the amino ketone, then condensed and then oxidized to a pyrazine. A variation is the Gutknecht pyrazine synthesis (1879) also based on this selfcondensation, but diff ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclohexadiene
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Cyclohexadiene may refer to: * 1,3-Cyclohexadiene, * 1,4-Cyclohexadiene, See also * Benzene or its theoretical isomer ''1,3,5-Cyclohexatriene'' * Cyclohexene Cyclohexene is a hydrocarbon with the formula C6H10. This cycloalkene is a colorless liquid with a sharp smell. It is an intermediate in various industrial processes. Cyclohexene is not very stable upon long term storage with exposure to light an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
4,4'-Bipyridine
4,4′-Bipyridine (abbreviated to 4,4′-bipy or 4,4′-bpy) is an organic compound with the formula . It is one of several isomers of bipyridine. It is a colorless solid that is soluble in organic solvents. is mainly used as a precursor to ''N'',''N''′-dimethyl-4,4′-bipyridinium C5H4NCH3)2sup>2+, known as paraquat. History 4,4′-Bipyridine was first obtained in 1868 by the Scottish chemist Thomas Anderson via heating pyridine with sodium metal. However, Anderson's empirical formula for 4,4′-bipyridine was incorrect. The correct empirical formula, and the correct molecular structure, for 4,4′-bipyridine was provided in 1882 by the Austrian chemist Hugo Weidel and his student M. Russo. Uses 4,4'-Bipyridine is an intermediate in the production of paraquat, a widely-used herbicide. In this process, pyridine is oxidized to 4,4'-bipyridine in a coupling reaction, followed by dimethylation to form paraquat. : Reactions The reducing agent is N,N'-bis(trimethylsil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trimethylsilyl Chloride
Trimethylsilyl chloride, also known as chlorotrimethylsilane is an organosilicon compound ( silyl halide), with the formula (CH3)3SiCl, often abbreviated Me3SiCl or TMSCl. It is a colourless volatile liquid that is stable in the absence of water. It is widely used in organic chemistry. Preparation TMSCl is prepared on a large scale by the '' direct process'', the reaction of methyl chloride with a silicon-copper alloy. The principal target of this process is dimethyldichlorosilane, but substantial amounts of the trimethyl and monomethyl products are also obtained. The relevant reactions are (Me = CH3): : x MeCl + Si → Me3SiCl, Me2SiCl2, MeSiCl3, other products Typically about 2–4% of the product stream is the monochloride, which forms an azeotrope with MeSiCl3. Reactions and uses TMSCl is reactive toward nucleophiles, resulting in the replacement of the chloride. In a characteristic reaction of TMSCl, the nucleophile is water, resulting in hydrolysis to give the hexamethy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tungsten Hexachloride
Tungsten hexachloride is the chemical compound of tungsten and chlorine with the formula WCl6. This dark violet blue species exists as a volatile solid under standard conditions. It is an important starting reagent in the preparation of tungsten compounds. Other examples of charge-neutral hexachlorides are rhenium(VI) chloride and molybdenum(VI) chloride. The highly volatile tungsten hexafluoride is also known. As a d0 ion, W(VI) forms diamagnetic derivatives. The hexachloride is octahedral with equivalent W–Cl distances of 2.24–2.26 Å. Preparation Tungsten hexachloride can be prepared by chlorinating tungsten metal in a sealed tube at 600 °C: : W + 3 Cl2 → WCl6 Properties and Reactions Tungsten (VI) chloride is a blue-black solid at room temperature. At lower temperatures, it becomes wine-red in color. A red form of the compound can be made by rapidly condensing its vapor, which reverts to the blue-black form on gentle heating. It is readily hydrolyzed, even ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Reactions
A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei (no change to the elements present), and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur. The substance (or substances) initially involved in a chemical reaction are called reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. Reactions often consist of a sequence of individual sub-steps, the so-called elementary reactions, and the information on the precise course of acti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Redox
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state. There are two classes of redox reactions: * ''Electron-transfer'' – Only one (usually) electron flows from the reducing agent to the oxidant. This type of redox reaction is often discussed in terms of redox couples and electrode potentials. * ''Atom transfer'' – An atom transfers from one substrate to another. For example, in the rusting of iron, the oxidation state of iron atoms increases as the iron converts to an oxide, and simultaneously the oxidation state of oxygen decreases as it accepts electrons released by the iron. Although oxidation reactions are commonly associated with the formation of oxides, other chemical species can serve the same function. In hydrogen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
