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Michaelis–Arbuzov Reaction
The Michaelis–Arbuzov reaction (also called the Arbuzov reaction) is the chemical reaction of a trivalent phosphorus ester with an alkyl halide to form a pentavalent phosphorus species and another alkyl halide. The picture below shows the most common types of substrates undergoing the Arbuzov reaction; phosphite esters (1) react to form phosphonates (2), phosphonites (3) react to form phosphinates (4) and phosphinites (5) react to form phosphine oxides (6). The reaction was discovered by August Michaelis in 1898, and greatly explored by Aleksandr Arbuzov soon thereafter. This reaction is widely used for the synthesis of various phosphonates, phosphinates, and phosphine oxides. Several reviews have been published. The reaction also occurs for coordinated phosphite ligands, as illustrated by the demethylation of 2+ to give −, which is called the Klaui ligand. Reaction mechanism file:Michaelis-Arbuzov Reaction Mechanism.png, center, 600px, The mechanism of the Michaelis–Arbu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
August Michaelis
August Michaelis (26 December 1847 – 31 January 1916) was a German chemist and discovered the Michaelis–Arbuzov reaction. Michaelis studied at the University of Göttingen and University of Jena and became professor for chemistry at University of Karlsruhe in 1876, at the University of Aachen in 1880, and at the University of Rostock The University of Rostock (german: link=no, Universität Rostock) is a public university located in Rostock, Mecklenburg-Vorpommern, Germany. Founded in 1419, it is the third-oldest university in Germany. It is the oldest university in continen ... in 1890. Works * ''Repetitorium und Examinatorium der Chemie'' . Laupp, Tübingen 185Digital editionby the University and State Library Düsseldorf * * References * * 1847 births 1916 deaths 19th-century German chemists People from the Kingdom of Hanover University of Göttingen alumni University of Jena alumni Academic staff of the Karlsruhe Institute of Technology Academic staff ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allyl Group
In organic chemistry, an allyl group is a substituent with the structural formula , where R is the rest of the molecule. It consists of a methylene bridge () attached to a vinyl group (). The name is derived from the scientific name for garlic, . In 1844, Theodor Wertheim isolated an allyl derivative from garlic oil and named it "". The term allyl applies to many compounds related to , some of which are of practical or of everyday importance, for example, allyl chloride. Allylation is any chemical reaction that adds an allyl group to a substrate. Nomenclature A site adjacent to the unsaturated carbon atom is called the allylic position or allylic site. A group attached at this site is sometimes described as allylic. Thus, "has an allylic hydroxyl group". Allylic C−H bonds are about 15% weaker than the C−H bonds in ordinary sp3 carbon centers and are thus more reactive. Benzylic and allylic are related in terms of structure, bond strength, and reactivity. Other ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allylic Rearrangement
An allylic rearrangement or allylic shift is an organic reaction in which the double bond in an allyl chemical compound shifts to the next carbon atom. It is encountered in nucleophilic substitution. In reaction conditions that favor a SN1 reaction mechanism, the intermediate is a carbocation for which several resonance structures are possible. This explains the product distribution (or product spread) after recombination with nucleophile Y. This type of process is called an SN1' substitution. Alternatively, it is possible for nucleophile to attack directly at the allylic position, displacing the leaving group in a single step, in a process referred to as SN2' substitution. This is likely in cases when the allyl compound is unhindered, and a strong nucleophile is used. The products will be similar to those seen with SN1' substitution. Thus reaction of 1-chloro-2-butene with sodium hydroxide gives a mixture of 2-buten-1-ol and 3-buten-2-ol: : Nevertheless, the product in whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aryl
In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used as a placeholder for the aryl group in chemical structure diagrams, analogous to “R” used for any organic substituent. “Ar” is not to be confused with the elemental symbol for argon. A simple aryl group is phenyl (), a group derived from benzene. Examples of other aryl groups consist of: * The tolyl group () which is derived from toluene (methylbenzene) * The xylyl group (), which is derived from xylene (dimethylbenzene) * The naphthyl group (), which is derived from naphthalene Arylation is the process in which an aryl group is attached to a substituent. It is typically achieved by cross-coupling reactions. Nomenclature The most basic aryl group is phenyl, which is made up of a benzene ring with one hydrogen atom substituted ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vinyl Group
In organic chemistry, a vinyl group (abbr. Vi; IUPAC name: ethenyl group) is a functional group with the formula . It is the ethylene (IUPAC name: ethene) molecule () with one fewer hydrogen atom. The name is also used for any compound containing that group, namely where R is any other group of atoms. An industrially important example is vinyl chloride, precursor to PVC, a plastic commonly known as ''vinyl''. Vinyl is one of the alkenyl functional groups. On a carbon skeleton, sp2-hybridized carbons or positions are often called vinylic. Allyls, acrylates and styrenics contain vinyl groups. (A styrenic crosslinker with two vinyl groups is called '' divinyl benzene''.) Vinyl polymers Vinyl groups can polymerize with the aid of a radical initiator or a catalyst, forming vinyl polymers. Vinyl polymers contain no vinyl groups. Instead they are saturated. The following table gives some examples of vinyl polymers. Reactivity Vinyl derivatives are alkenes. If activated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microscopic Reversibility
The principle of microscopic reversibility in physics and chemistry is twofold: * First, it states that the microscopic detailed dynamics of particles and fields is time-reversible because the microscopic equations of motion are symmetric with respect to inversion in time (T-symmetry); * Second, it relates to the statistical description of the kinetics of macroscopic or mesoscopic systems as an ensemble of elementary processes: collisions, elementary transitions or reactions. For these processes, the consequence of the microscopic T-symmetry is: ''Corresponding to every individual process there is a reverse process, and in a state of equilibrium the average rate of every process is equal to the average rate of its reverse process.'' History of microscopic reversibility The idea of microscopic reversibility was born together with physical kinetics. In 1872, Ludwig Boltzmann represented kinetics of gases as statistical ensemble of elementary collisions.Boltzmann, L. (1964), Lectures on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neopentyl
Pentyl is a five-carbon alkyl group or substituent with chemical formula -C5H11. It is the substituent form of the alkane pentane. In older literature, the common non-systematic name amyl was often used for the pentyl group. Conversely, the name pentyl was used for several five-carbon branched alkyl groups, distinguished by various prefixes. The nomenclature has now reversed, with "amyl" being more often used to refer to the terminally branched group also called isopentyl, as in amobarbital. A cyclopentyl group is a ring with the formula -C5H9. The name is also used for the pentyl radical, a pentyl group as an isolated molecule. This free radical is only observed in extreme conditions. Its formula is often written "•" or "• " to indicate that it has one unsatisfied valence bond. Older "pentyl" groups The following names are still used sometimes: Pentyl radical The free radical pentyl was studied by J. Pacansky and A. Gutierrez in 1983. The radical was obtained by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SN1 Reaction
The SN1 reaction is a substitution reaction in organic chemistry, the name of which refers to the Hughes-Ingold symbol of the mechanism. "SN" stands for "nucleophilic substitution", and the "1" says that the rate-determining step is unimolecular. Thus, the rate equation is often shown as having first-order dependence on the substrate and zero-order dependence on the nucleophile. This relationship holds for situations where the amount of nucleophile is much greater than that of the intermediate. Instead, the rate equation may be more accurately described using steady-state kinetics. The reaction involves a carbocation intermediate and is commonly seen in reactions of secondary or tertiary alkyl halides under strongly basic conditions or, under strongly acidic conditions, with secondary or tertiary alcohols. With primary and secondary alkyl halides, the alternative SN2 reaction occurs. In inorganic chemistry, the SN1 reaction is often known as the ''dissociative substitution''. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbocation
A carbocation is an ion with a positively charged carbon atom. Among the simplest examples are the methenium , methanium and vinyl cations. Occasionally, carbocations that bear more than one positively charged carbon atom are also encountered (e.g., ethylene dication ). Until the early 1970s, all carbocations were called ''carbonium ions''. In the present-day definition given by the IUPAC, a carbocation is any even-electron cation with significant partial positive charge on a carbon atom. They are further classified in two main categories according to the coordination number of the charged carbon: three in the carbenium ions and five in the carbonium ions. This nomenclature was proposed by G. A. Olah. Carbonium ions, as originally defined by Olah, are characterized by a three-center two-electron delocalized bonding scheme and are essentially synonymous with so-called 'non-classical carbocations', which are carbocations that contain bridging C–C or C–H σ-bonds. Howe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halide
In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluoride, chloride, bromide, iodide, astatide, or theoretically tennesside compound. The alkali metals combine directly with halogens under appropriate conditions forming halides of the general formula, MX (X = F, Cl, Br or I). Many salts are halides; the ''hal-'' syllable in ''halide'' and ''halite'' reflects this correlation. All Group 1 metals form halides that are white solids at room temperature. A halide ion is a halogen atom bearing a negative charge. The halide anions are fluoride (), chloride (), bromide (), iodide () and astatide (). Such ions are present in all ionic halide salts. Halide minerals contain halides. All these halides are colourless, high melting crystalline solids having high negative enthalpies of formation. Test ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphonium Salt
In polyatomic cations with the chemical formula (where R is a hydrogen or an alkyl, aryl, or halide group). These cations have tetrahedral structures. The salts are generally colorless or take the color of the anions. Types of phosphonium cations Protonated phosphines The parent phosphonium is as found in the iodide salt, phosphonium iodide. Salts of the parent are rarely encountered, but this ion is an intermediate in the preparation of the industrially useful tetrakis(hydroxymethyl)phosphonium chloride: :PH3 + HCl + 4 CH2O → Many organophosphonium salts are produced by protonation of primary, secondary, and tertiary phosphines: :PR3 + H+ → The basicity of phosphines follows the usual trends, with R = alkyl being more basic than R = aryl. Tetraorganophosphonium cations The most common phosphonium compounds have four organic substituents attached to phosphorus. The quaternary phosphonium cations include tetraphenylphosphonium, (C6H5)4P+ and tetramethylphosphonium ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
