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Diethylaluminium Chloride
Diethylaluminium chloride, abbreviated DEAC, is an organoaluminium compound. Although often given the chemical formula (C2H5)2AlCl, it exists as a dimer, C2H5)2AlClsub>2 It is a precursor to Ziegler–Natta catalysts employed for the production of polyolefins. The compound is also a Lewis acid, useful in organic synthesis. The compound is a colorless waxy solid, but is usually handled as a solution in hydrocarbon solvents. It is highly reactive, even pyrophoric. Structure and bonding Compounds of the empirical formula AlR2Cl (R = alkyl, aryl) usually exist as dimers with the formula (R2Al)2(μ-Cl)2. The bridging ligands (indicated by "μ-") are halides, not the organic substituents. The aluminium adopts a tetrahedral geometry. Each Al(III) center follows the octet rule. In contrast, triethylaluminium and trimethylaluminium feature bridging alkyl groups and these compounds violate the octet rule. Production Diethylaluminium chloride can be produced from ethylaluminium sesquich ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organoaluminium Compound
Organoaluminium chemistry is the study of compounds containing bonds between carbon and aluminium. It is one of the major themes within organometallic chemistry. Illustrative organoaluminium compounds are the dimer trimethylaluminium, the monomer triisobutylaluminium, and the titanium-aluminium compound called Tebbe's reagent. The behavior of organoaluminium compounds can be understood in terms of the polarity of the C−Al bond and the high Lewis acidity of the three-coordinated species. Industrially, these compounds are mainly used for the production of polyolefins. History The first organoaluminium compound (C2H5)3Al2I3 was discovered in 1859. Organoaluminium compounds were, however, little known until the 1950s when Karl Ziegler and colleagues discovered the direct synthesis of trialkylaluminium compounds and applied these compounds to catalytic olefin polymerization. This line of research ultimately resulted in the Nobel Prize to Ziegler. Structure and bonding Aluminium( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Octet Rule
The octet rule is a chemical rule of thumb that reflects the theory that main-group elements tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas. The rule is especially applicable to carbon, nitrogen, oxygen, and the halogens; although more generally the rule is applicable for the s-block and p-block of the periodic table. Other rules exist for other elements, such as the duplet rule for hydrogen and helium, and the 18-electron rule for transition metals. The valence electrons in molecules like carbon dioxide (CO₂) can be visualized using a Lewis electron dot diagram. In covalent bonds, electrons shared between two atoms are counted toward the octet of both atoms. In carbon dioxide each oxygen shares four electrons with the central carbon, two (shown in red) from the oxygen itself and two (shown in black) from the carbon. All four of these electrons are counted in both the carbon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organoaluminium Compounds
Organoaluminium chemistry is the study of compounds containing bonds between carbon and aluminium. It is one of the major themes within organometallic chemistry. Illustrative organoaluminium compounds are the dimer trimethylaluminium, the monomer triisobutylaluminium, and the titanium-aluminium compound called Tebbe's reagent. The behavior of organoaluminium compounds can be understood in terms of the polarity of the C−Al bond and the high Lewis acidity of the three-coordinated species. Industrially, these compounds are mainly used for the production of polyolefins. History The first organoaluminium compound (C2H5)3Al2I3 was discovered in 1859. Organoaluminium compounds were, however, little known until the 1950s when Karl Ziegler and colleagues discovered the direct synthesis of trialkylaluminium compounds and applied these compounds to catalytic olefin polymerization. This line of research ultimately resulted in the Nobel Prize to Ziegler. Structure and bonding Alumini ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ene Reaction
In organic chemistry, the ene reaction (also known as the Alder-ene reaction by its discoverer Kurt Alder in 1943) is a chemical reaction between an alkene with an allylic hydrogen (the ene) and a compound containing a multiple bond (the enophile), in order to form a new σ-bond with migration of the ene double bond and 1,5 hydrogen shift. The product is a substituted alkene with the double bond shifted to the allylic position. This transformation is a group transfer pericyclic reaction, and therefore, usually requires highly activated substrates and/or high temperatures. Nonetheless, the reaction is compatible with a wide variety of functional groups that can be appended to the ene and enophile moieties. Many useful Lewis acid-catalyzed ene reactions have been also developed, which can afford high yields and selectivities at significantly lower temperatures. Ene component Enes are π-bonded molecules that contain at least one hydrogen atom at the allylic, propargylic, or � ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diels–Alder Reaction
In organic chemistry, the Diels–Alder reaction is a chemical reaction between a Conjugated system, conjugated diene and a substituted alkene, commonly termed the Diels–Alder reaction#The dienophile, dienophile, to form a substituted cyclohexene derivative. It is the prototypical example of a pericyclic reaction with a concerted reaction, concerted mechanism. More specifically, it is classified as a thermally allowed [4+2] cycloaddition with Woodward–Hoffmann rules, Woodward–Hoffmann symbol [π4s + π2s]. It was first described by Otto Diels and Kurt Alder in 1928. For the discovery of this reaction, they were awarded the Nobel Prize in Chemistry in 1950. Through the simultaneous construction of two new carbon–carbon bonds, the Diels–Alder reaction provides a reliable way to form six-membered rings with good control over the regio- and stereochemical outcomes. Consequently, it has served as a powerful and widely applied tool for the introduction of chemical complexity in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ethylaluminium Sesquichloride
Ethylaluminium sesquichloride, also called EASC, is an industrially important organoaluminium compound used primarily as a precursor to triethylaluminium and as a catalyst component in Ziegler–Natta type systems for olefin and diene polymerizations. Other applications include use in alkylation reactions and as a catalyst component in linear oligomerization and cyclization of unsaturated hydrocarbons. EASC is a colourless liquid, spontaneously combustible in air and reacts violently when in contact with water and many other compounds.Aluminum alkyls. Albemarle Corporation 2010 Production Methyl, ethyl, and other alkyl or aralkyl halides that are not dehydrohalogenated readily can react with aluminium in an exothermic process to form organoaluminiu ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trimethylaluminium
Trimethylaluminium or TMA is one of the simplest examples of an organoaluminium compound. Despite its name it has the formula (abbreviated as , where Me stands for methyl), as it exists as a dimer. This colorless liquid is pyrophoric. It is an industrially important compound, closely related to triethylaluminium. Structure and bonding The structure and bonding in and diborane are analogous (R = alkyl). In , the Al-C(terminal) and Al-C(bridging) distances are 1.97 and 2.14 Å, respectively. The Al center is tetrahedral. The carbon atoms of the bridging methyl groups are each surrounded by five neighbors: three hydrogen atoms and two aluminium atoms. The methyl groups interchange readily intramolecularly. At higher temperatures, the dimer cracks into monomeric . Synthesis TMA is prepared via a two-step process that can be summarized as follows: : Applications Catalysis Starting with the invention of Ziegler-Natta catalysis, organoaluminium compounds have a prominent role ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triethylaluminium
Triethylaluminium is one of the simplest examples of an organoaluminium compound. Despite its name the compound has the formula Al2( C2H5)6 (abbreviated as Al2Et6 or TEA). This colorless liquid is pyrophoric. It is an industrially important compound, closely related to trimethylaluminium. Structure and bonding The structure and bonding in Al2R6 and diborane are analogous (R = alkyl). Referring to Al2Me6, the Al-C(terminal) and Al-C(bridging) distances are 1.97 and 2.14 Å, respectively. The Al center is tetrahedral. The carbon atoms of the bridging ethyl groups are each surrounded by five neighbors: carbon, two hydrogen atoms and two aluminium atoms. The ethyl groups interchange readily intramolecularly. At higher temperatures, the dimer cracks into monomeric AlEt3. Synthesis and reactions Triethylaluminium can be formed via several routes. The discovery of an efficient route was a significant technological achievement. The multistep process uses aluminium, hydrogen gas, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bridging Ligand
In coordination chemistry, a bridging ligand is a ligand that connects two or more atoms, usually metal ions. The ligand may be atomic or polyatomic. Virtually all complex organic compounds can serve as bridging ligands, so the term is usually restricted to small ligands such as pseudohalides or to ligands that are specifically designed to link two metals. In naming a complex wherein a single atom bridges two metals, the bridging ligand is preceded by the Greek letter mu, μ, with a subscript number denoting the number of metals bound to the bridging ligand. μ2 is often denoted simply as μ. When describing coordination complexes care should be taken not to confuse μ with η ('eta'), which relates to hapticity. Ligands that are not bridging are called terminal ligands. List of bridging ligands Virtually all ligands are known to bridge, with the exception of amines and ammonia. Common bridging ligands include most of the common anions. Many simple organic ligands form s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Formula
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and ''plus'' (+) and ''minus'' (−) signs. These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a chemical name since it does not contain any words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulae can fully specify the structure of only the simplest of molecules and chemical substances, and are generally more limited in power than chemical names and structural formulae. The simplest types of chemical formulae are called '' empirical formulae'', which use letters and numbers indicating the numerical ''proportions'' of atoms ... [...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 simplest aryl group is phenyl, which is made up of a benzene ring with one of its hydrogen atom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkyl
In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl group is derived from a cycloalkane by removal of a hydrogen atom from a Ring (chemistry), ring and has the general formula . Typically an alkyl is a part of a larger molecule. In structural formulae, the symbol R is used to designate a generic (unspecified) alkyl group. The smallest alkyl group is methyl, with the formula . Related concepts Alkylation is the addition of alkyl groups to molecules, often by alkylating agents such as Haloalkane, alkyl halides. Alkylating antineoplastic agents are a class of compounds that are used to treat cancer. In such case, the term alkyl is used loosely. For example, nitrogen mustards are well-known alkylating agents, but they are not simple hydrocarbons. In chemistry, alkyl is a group, a substituent, that is attached to ot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
