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Radical Fluorination
Radical fluorination is a type of fluorination reaction, complementary to nucleophilic and electrophilic approaches. It involves the reaction of an independently generated carbon-centered radical with an atomic fluorine source and yields an organofluorine compound. : Historically, only three atomic fluorine sources were available for radical fluorination: Fluorine (F2), hypofluorites (O–F based reagents) and XeF2. Their high reactivity, and the difficult handling of F2 and the hypofluorites, limited the development of radical fluorination compared to electrophilic and nucleophilic methods. The uncovering of the ability of electrophilic N–F fluorinating agents to act as an atomic fluorine source led to a renaissance in radical fluorination. Various methodologies have since been developed for the radical formation of C–F bonds. The radical intermediates have been generated from carboxylic acids and boronic acid derivatives, by radical addition to alkenes, or C–H and C–C bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorination
In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drugs. This kind of conversion is in fact so common that a comprehensive overview is challenging. This article mainly deals with halogenation using elemental halogens (F2, Cl2, Br2, I2). Halides are also commonly introduced using salts of the halides and halogen acids. Many specialized reagents exist for and introducing halogens into diverse substrates, e.g. thionyl chloride. Organic chemistry Several pathways exist for the halogenation of organic compounds, including free radical halogenation, ketone halogenation, electrophilic halogenation, and halogen addition reaction. The nature of the substrate determines the pathway. The facility of halogenation is influenced by the halogen. Fluorine and chlorine are more electrophilic and are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hunsdiecker Reaction
The Hunsdiecker reaction (also called the Borodin reaction or the Hunsdiecker–Borodin reaction) is a name reaction in organic chemistry whereby silver salts of carboxylic acids react with a halogen to produce an organic halide. It is an example of both a decarboxylation and a halogenation reaction as the product has one fewer carbon atoms than the starting material (lost as carbon dioxide) and a halogen atom is introduced its place. The reaction was first demonstrated by Alexander Borodin in his 1861 reports of the preparation of methyl bromide () from silver acetate (). Shortly after, the approach was applied to the degradation of fatty acids in the laboratory of Adolf Lieben. However, it is named for Cläre Hunsdiecker and her husband Heinz Hunsdiecker, whose work in the 1930s developed it into a general method. Several reviews have been published, and a catalytic approach has been developed. : History Alexander Borodin first observed the reaction in 1861 when he prep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoredox Catalysis
Photoredox catalysis is a branch of photochemistry that uses single-electron transfer. Photoredox catalysts are generally drawn from three classes of materials: transition-metal complexes, organic dyes, and semiconductors. While organic photoredox catalysts were dominant throughout the 1990s and early 2000s, soluble transition-metal complexes are more commonly used today. Photochemistry of transition metal sensitizers Sensitizers absorb light to give redox-active excited states. For many metal-based sensitizers, excitation is realized as a metal-to-ligand charge transfer, whereby an electron moves from the metal (e.g., a d orbital) to an orbital localized on the ligands (e.g. the π* orbital of an aromatic ligand). The initial excited electronic state relaxes to the lowest energy singlet excited state through internal conversion, a process where energy is dissipated as vibrational energy rather than as electromagnetic radiation. This singlet excited state can relax further by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Manganese
Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy uses, particularly in stainless steels. It improves strength, workability, and resistance to wear. Manganese oxide is used as an oxidising agent; as a rubber additive; and in glass making, fertilisers, and ceramics. Manganese sulfate can be used as a fungicide. Manganese is also an essential human dietary element, important in macronutrient metabolism, bone formation, and free radical defense systems. It is a critical component in dozens of proteins and enzymes. It is found mostly in the bones, but also the liver, kidneys, and brain. In the human brain, the manganese is bound to manganese metalloproteins, most notably glutamine synthetase in astrocytes. Manganese was first isolated in 1774. It is familiar in the laboratory in the form of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silver
Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. The metal is found in the Earth's crust in the pure, free elemental form ("native silver"), as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. Most silver is produced as a byproduct of copper, gold, lead, and zinc Refining (metallurgy), refining. Silver has long been valued as a precious metal. Silver metal is used in many bullion coins, sometimes bimetallism, alongside gold: while it is more abundant than gold, it is much less abundant as a native metal. Its purity is typically measured on a per-mille basis; a 94%-pure alloy is described as "0.940 fine". As one of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboxylic Acid
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion. Examples and nomenclature Carboxylic acids are commonly identified by their trivial names. They at oftentimes have the suffix ''-ic acid''. IUPAC-recommended names also exist; in this system, carboxylic acids have an ''-oic acid'' suffix. For example, butyric acid (C3H7CO2H) is butanoic acid by IUPAC guidelines. For nomenclature of complex molecules containing a carboxylic acid, the carboxyl can be considered position one of the parent chain even if there are other substituents, such as 3-chloropropanoic acid. Alternately, it can be named as a "carboxy" or "carboxylic acid" substituent on another ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perester
In organic chemistry, organic peroxides are organic compounds containing the peroxide functional group (). If the R′ is hydrogen, the compounds are called hydroperoxides, which are discussed in that article. The O−O bond of peroxides easily breaks, producing free radicals of the form (the dot represents an unpaired electron). Thus, organic peroxides are useful as initiators for some types of polymerisation, such as the epoxy resins used in glass-reinforced plastics. MEKP and benzoyl peroxide are commonly used for this purpose. However, the same property also means that organic peroxides can explosively combust. Organic peroxides, like their inorganic counterparts, are often powerful bleaching agents. Types of organic peroxides Tert-Butyl hydroperoxide Structural Formula V2.svg, ''tert''-Butyl hydroperoxide, a hydroperoxide (formula: ROOH) that is used to epoxide alkenes. Dicumyl peroxide.svg, Dicumyl peroxide, a dialkyl peroxide (formula: ROOR) that is used to initiate po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perester
In organic chemistry, organic peroxides are organic compounds containing the peroxide functional group (). If the R′ is hydrogen, the compounds are called hydroperoxides, which are discussed in that article. The O−O bond of peroxides easily breaks, producing free radicals of the form (the dot represents an unpaired electron). Thus, organic peroxides are useful as initiators for some types of polymerisation, such as the epoxy resins used in glass-reinforced plastics. MEKP and benzoyl peroxide are commonly used for this purpose. However, the same property also means that organic peroxides can explosively combust. Organic peroxides, like their inorganic counterparts, are often powerful bleaching agents. Types of organic peroxides Tert-Butyl hydroperoxide Structural Formula V2.svg, ''tert''-Butyl hydroperoxide, a hydroperoxide (formula: ROOH) that is used to epoxide alkenes. Dicumyl peroxide.svg, Dicumyl peroxide, a dialkyl peroxide (formula: ROOR) that is used to initiate po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tert-Butyl
In organic chemistry, butyl is a four-carbon alkyl radical or substituent group with general chemical formula , derived from either of the two isomers (''n''-butane and isobutane) of butane. The isomer ''n''-butane can connect in two ways, giving rise to two "-butyl" groups: * If it connects at one of the two terminal carbon atoms, it is normal butyl or ''n''-butyl: (preferred IUPAC name: butyl) * If it connects at one of the non-terminal (internal) carbon atoms, it is secondary butyl or ''sec''-butyl: (preferred IUPAC name: butan-2-yl) The second isomer of butane, isobutane, can also connect in two ways, giving rise to two additional groups: * If it connects at one of the three terminal carbons, it is isobutyl: (preferred IUPAC name: 2-methylpropyl) * If it connects at the central carbon, it is tertiary butyl, ''tert''-butyl or ''t''-butyl: (preferred IUPAC name: ''tert''-butyl) Nomenclature According to IUPAC nomenclature, "isobutyl", "''sec''-butyl", and "''tert''-b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Decomposition
Thermal decomposition, or thermolysis, is a chemical decomposition caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. If decomposition is sufficiently exothermic, a positive feedback loop is created producing thermal runaway and possibly an explosion or other chemical reaction. Decomposition temperature definition A simple substance (like water) may exist in equilibrium with its thermal decomposition products, effectively halting the decomposition. The equilibrium fraction of decomposed molecules increases with the temperature. Examples * Calcium carbonate (limestone or chalk) decomposes into calcium oxide and carbon dioxide when heated. The chemical reaction is as follows: ::CaCO3 → CaO + CO2 :The reaction is used to make Calcium oxide, quick lime, which is an industrially impor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bromine Trifluoride
Bromine trifluoride is an interhalogen compound with the formula BrF3. At room temperature, it is a straw-coloured liquid with a pungent odor which decomposes violently on contact with water and organic compounds. It is a powerful fluorinating agent and an ionizing inorganic solvent. It is used to produce uranium hexafluoride (UF6) in the processing and reprocessing of nuclear fuel. Synthesis Bromine trifluoride was first described by Paul Lebeau in 1906, who obtained the material by the reaction of bromine with fluorine at 20 °C: : The disproportionation of bromine monofluoride also gives bromine trifluoride: : Structure Like ClF3 and IF3, the BrF3 molecule is T-shaped and planar. In the VSEPR formalism, the bromine center is assigned two electron pairs. The distance from the bromine each axial fluorine is 1.81 Å and to the equatorial fluorine is 1.72 Å. The angle between an axial fluorine and the equatorial fluorine is slightly smaller than 90° — the 86.2° ang ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selectfluor
Selectfluor, a trademark of Air Products and Chemicals, is a reagent in chemistry that is used as a fluorine donor. This compound is a derivative of the nucleophillic base DABCO. It is a colourless salt that tolerates air and even water. It has been commercialized for use for electrophilic fluorination. Preparation Selectfluor is synthesized by the ''N''-alkylation of diazabicyclo .2.2ctane (DABCO) with dichloromethane, followed by ion exchange with sodium tetrafluoroborate (replacing the chloride counterion for the tetrafluoroborate). The resulting salt is treated with elemental fluorine and sodium tetrafluoroborate: : Mechanism of fluorination Electrophilic fluorinating reagents could in principle operate by electron transfer pathways or an SN2 attack at fluorine. This distinction has not been decided. By using a charge-spin separated probe, it was possible to show that the electrophilic fluorination of stilbenes with Selectfluor proceeds through an SET/fluorine atom tran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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