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Tert-butoxide
Potassium ''tert''-butoxide is the chemical compound with the formula K+(CH3)3CO−. This colourless solid is a strong base (pKa of conjugate acid around 17), which is useful in organic synthesis. It exists as a tetrameric cubane-type cluster. It is often seen written in chemical literature as potassium ''t''-butoxide. The compound is often depicted as a salt, and it often behaves as such, but it is not ionized in solution. Preparation Potassium ''t''-butoxide is commercially available as a solution and as a solid, but it is often generated ''in situ'' for laboratory use because samples are so sensitive and older samples are often of poor quality. It is prepared by the reaction of dry ''tert''-butyl alcohol with potassium metal. The solid is obtained by evaporating these solutions followed by heating the solid. The solid can be purified by sublimation at 220 °C and 1 mmHg. Sublimation can also take place at 140 °C and 0.01 hPa. It is advisable to cover the r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Tert-butoxide
Sodium ''tert''-butoxide is the chemical compound with the formula (CH3)3CONa. It is a strong base and a non-nucleophilic base. It is flammable and moisture sensitive. It is sometimes written in chemical literature as sodium ''t''-butoxide. It is similar in reactivity to the more common potassium ''tert''-butoxide. The compound can be produced by treating ''tert''-butyl alcohol with sodium hydride. Reactions One application for sodium ''tert''-butoxide is as a non-nucleophilic base. It has been widely used in the Buchwald–Hartwig amination, as in this typical example: Sodium tert-butoxide is used to prepare tert-butoxide complexes. For example hexa(tert-butoxy)ditungsten(III) is thus converted by the salt metathesis reaction from a ditungsten heptachloride: :NaW2Cl7(THF)5 + 6 NaOBu-t → W2(OBu-t)6 + 7 NaCl + 5 THF Structure Sodium ''tert''-butoxide forms clusters in the solid state, both hexamers and nonamers. {, class="wikitable" style="text-align:center;" , ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithium Tert-butoxide
Lithium ''tert''-butoxide is the metalloorganic compound with the formula LiOC(CH3)3. A white solid, it is used as a strong base in organic synthesis. The compound is often depicted as a salt, and it often behaves as such, but it is not ionized in solution. Both octameric and hexameric forms have been characterized by X-ray crystallography Preparation Lithium ''tert''-butoxide is commercially available as a solution and as a solid, but it is often generated ''in situ'' for laboratory use because samples are so sensitive and older samples are often of poor quality. It can be obtained by treating tert-butanol with butyl lithium. Reactions As a strong base, lithium ''tert''-butoxide is easily protonated. Lithium ''tert''-butoxide is used to prepare other ''tert''-butoxide compounds such as copper(I) t-butoxide and hexa(tert-butoxy)dimolybdenum(III): :2 MoCl3(thf)3 + 6 LiOBu-t → Mo2(OBu-t)6 + 6 LiCl + 6 thf Related compounds *Sodium tert-butoxide *Potassium tert-butox ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schlosser's Base
Schlosser's base (or Lochmann-Schlosser base) describes various superbasic mixtures of an alkyllithium compound and a potassium alkoxide. The reagent is named after Manfred Schlosser, although he uses the term ''LICKOR superbase'' (LIC denoting the alkyllithium, and KOR denoting the potassium alkoxide). The superbasic nature of the reagent is a consequence of the ''in situ'' formation of the corresponding organopotassium compound Organosodium chemistry is the chemistry of organometallic compounds containing a carbon to sodium chemical bond. The application of organosodium compounds in chemistry is limited in part due to competition from organolithium compounds, which are ..., as well as changes to the aggregation state of the alkyllithium species. Preparation and reactivity Commonly, the mixture called Schlosser's base is produced by combining ''n''-butyllithium and potassium ''tert''-butoxide in a one-to-one ratio. The high reactivity of Schlosser's base is exploited in s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dehydrohalogenation
In chemistry, dehydrohalogenation is an elimination reaction which removes a hydrogen halide from a substrate. The reaction is usually associated with the synthesis of alkenes, but it has wider applications. Dehydrohalogenation from alkyl halides Traditionally, alkyl halides are substrates for dehydrohalogenations. The alkyl halide must be able to form an alkene, thus halides having no C–H bond on an adjacent carbon are not suitable substrates. Aryl halides are also unsuitable. Upon treatment with strong base, chlorobenzene dehydrohalogenates to give phenol via a benzyne intermediate. Base-promoted reactions to alkenes When treated with a strong base many alkyl chlorides convert to corresponding alkene. It is also called a β-elimination reaction and is a type of elimination reaction. Some prototypes are shown below: :\begin \ce\ &\ce \\ \ce\ &\ce \\ \ce\ &\ce \end Here ethyl chloride reacts with potassium hydroxide, typically in a solvent such as ethanol, giving ethylene. Li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkoxides
In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as , where R is the organic substituent. Alkoxides are strong bases and, when R is not bulky, good nucleophiles and good ligands. Alkoxides, although generally not stable in protic solvents such as water, occur widely as intermediates in various reactions, including the Williamson ether synthesis. Transition metal alkoxides are widely used for coatings and as catalysts. Enolates are unsaturated alkoxides derived by deprotonation of a bond adjacent to a ketone or aldehyde. The nucleophilic center for simple alkoxides is located on the oxygen, whereas the nucleophilic site on enolates is delocalized onto both carbon and oxygen sites. Ynolates are also unsaturated alkoxides derived from acetylenic alcohols. Phenoxides are close relatives of the alkoxides, in which the alkyl group is replaced by a derivative o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tert-Butanol
''tert''-Butyl alcohol is the simplest tertiary alcohol, with a formula of (CH3)3COH (sometimes represented as ''t''-BuOH). Its isomers are 1-butanol, isobutanol, and butan-2-ol. ''tert''-Butyl alcohol is a colorless solid, which melts near room temperature and has a camphor-like odor. It is miscible with water, ethanol and diethyl ether. Natural occurrence ''tert''-Butyl alcohol has been identified in beer and chickpeas. It is also found in cassava, which is used as a fermentation ingredient in certain alcoholic beverages. Preparation ''tert''-Butyl alcohol is derived commercially from isobutane as a coproduct of propylene oxide production. It can also be produced by the catalytic hydration of isobutylene, or by a Grignard reaction between acetone and methylmagnesium chloride. Purification cannot be performed by simple distillation due to formation of an azeotrope with water, although initial drying of the solvent containing large amounts of water is performed by adding benz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elimination Reaction
An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one- or two-step mechanism. The one-step mechanism is known as the E2 reaction, and the two-step mechanism is known as the E1 reaction. The numbers refer not to the number of steps in the mechanism, but rather to the kinetics of the reaction: E2 is bimolecular (second-order) while E1 is unimolecular (first-order). In cases where the molecule is able to stabilize an anion but possesses a poor leaving group, a third type of reaction, E1CB, exists. Finally, the pyrolysis of xanthate and acetate esters proceed through an "internal" elimination mechanism, the Ei mechanism. E2 mechanism The E2 mechanism, where E2 stands for bimolecular elimination, involves a one-step mechanism in which ''carbon-hydrogen'' and ''carbon-halogen'' bonds break to form a double bond (''C=C Pi bond''). The specifics of the reaction are as follows: * E2 is a single step elimination, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dichlorocarbene
Dichlorocarbene is the reactive intermediate with chemical formula CCl2. Although this chemical species has not been isolated, it is a common intermediate in organic chemistry, being generated from chloroform. This bent diamagnetic molecule rapidly inserts into other bonds. Preparation Dichlorocarbene is most commonly generated by reaction of chloroform and a base such as potassium ''tert''-butoxide or aqueous sodium hydroxide. A phase transfer catalyst, for instance benzyltriethylammonium bromide, facilitates the migration of the hydroxide in the organic phase. :HCCl3 + NaOH → CCl2 + NaCl + H2O Other reagents and routes Another precursor to dichlorocarbene is ethyl trichloroacetate. Upon treatment with sodium methoxide it releases CCl2. Phenyl(trichloromethyl)mercury decomposes thermally to release CCl2. :PhHgCCl3 → CCl2 + PhHgCl Dichlorodiazirine, which is stable in the dark, decomposes into dichlorocarbene and nitrogen via photolysis. Dichlorocarbene can also be obta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silanes
Silanes refers to diverse kinds of charge-neutral silicon compounds with the formula . The R substituents can any combination of organic or inorganic groups. Most silanes contain Si-C bonds, and are discussed under organosilicon compounds. Examples: *Silane , the parent. *Binary silicon-hydrogen compounds (which are sometimes called silanes also) includes silane itself but also compounds with Si-Si bonds including disilane and longer chains. *Silanes with one, two, three, or four Si-H bonds are called hydrosilanes. Silane itself is the parent member. Examples: triethylsilane () and triethoxysilane (). *Polysilanes are organosilicon compounds with the formula . They include all binary silicon-hydrogen compounds except the parent, although these tend to be less useful because they are fragile. Attracting more interest, are the organic derivatives such as polydimethylsilane and dodecamethylcyclohexasilane *Chlorosilanes have Si-Cl bonds. Examples: trichlorosilane () and tetrachlo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkene
In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, and Biological Chemistry'. 1232 pages. Two general types of monoalkenes are distinguished: terminal and internal. Also called α-olefins, terminal alkenes are more useful. However, the International Union of Pure and Applied Chemistry (IUPAC) recommends using the name "alkene" only for acyclic hydrocarbons with just one double bond; alkadiene, alkatriene, etc., or polyene for acyclic hydrocarbons with two or more double bonds; cycloalkene, cycloalkadiene, etc. for cyclic ones; and "olefin" for the general class – cyclic or acyclic, with one or more double bonds. Acyclic alkenes, with only one double bond and no other functional groups (also known as mono-enes) form a homologous series of hydrocarbons with the general formula with '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
18-crown-6
18-Crown-6 is an organic compound with the formula [C2H4O]6 and the IUPAC name of 1,4,7,10,13,16-hexaoxacyclooctadecane. It is a white, hygroscopic crystalline solid with a low melting point. Like other crown ethers, 18-crown-6 functions as a ligand for some metal cations with a particular affinity for potassium cations (binding constant in methanol: 106 M−1). The point group of 18-crown-6 is S6. The dipole moment of 18-crown-6 varies in different solvent and under different temperature. Under 25 °C, the dipole moment of 18-crown-6 is in cyclohexane and in benzene. The synthesis of the crown ethers led to the awarding of the Nobel Prize in Chemistry to Charles J. Pedersen. Synthesis This compound is prepared by a modified Williamson ether synthesis in the presence of a templating cation: It can be also prepared by the oligomerization of ethylene oxide: :(CH2OCH2CH2Cl)2 + (CH2OCH2CH2OH)2 + 2 KOH → (CH2CH2O)6 + 2 KCl + 2 H2O It can be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hexamethylphosphoramide
Hexamethylphosphoramide, often abbreviated HMPA, is a phosphoramide (an amide of phosphoric acid) with the formula This colorless liquid is a useful reagent in organic synthesis. Structure and reactivity HMPA is the oxide of the highly basic tertiary phosphine hexamethylphosphorous triamide (HMPT), P(NMe2)3. Like other phosphine oxides (such as triphenylphosphine oxide), the molecule has a tetrahedral core and a P=O bond that is highly polarized, with significant negative charge residing on the oxygen atom. Compounds containing a nitrogen–phosphorus bond typically are degraded by hydrochloric acid to form a protonated amine and phosphate. It dissolves alkali metal salts and alkali metals, forming blue solutions which are stable for a few hours. Solvated electrons are present in these blue solutions. Applications HMPA is a specialty solvent for polymers, gases, and organometallic compounds. It improves the selectivity of lithiation reactions by breaking up the oligomers of lit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
