|
Steglich Esterification
The Steglich esterification is a variation of an esterification with dicyclohexylcarbodiimide as a coupling reagent and 4-dimethylaminopyridine as a catalyst. The reaction was first described by Wolfgang Steglich in 1978. It is an adaptation of an older method for the formation of amides by means of DCC (dicyclohexylcarbodiimide) and 1-hydroxybenzotriazole (HOBT). : This reaction generally takes place at room temperature. A suitable solvent is dichloromethane. Because the reaction is mild, esters can be obtained that are inaccessible through other methods for instance esters of the sensitive 2,4-dihydroxybenzoic acid. A characteristic is the formal uptake of water generated in the reaction by DCC, forming the urea compound dicyclohexylurea (DCU). Reaction mechanism The reaction mechanism is described as follows: With amines, the reaction proceeds without problems to the corresponding amides because amines are more nucleophilic. If the esterification is slow, a side-reactio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wolfgang Steglich
Wolfgang Steglich (born 12 August 1933) is a German chemist . Life Wolfgang Steglich was born in Kamenz and studied chemistry at the Technical University of Berlin and later at the Technical University of Munich where he received his PhD in 1960 for work with Friedrich Weygand. Following a postdoc stay with Sir Derek H. R. Barton at the Imperial College London, Wolfgang Steglich completed his habilitation at the Technical University of Munich. After Friedrich Weygand's decease in 1969, Steglich was in charge of the Weygand chair until he became a full professor at the Technical University of Berlin in 1971. In 1975, he was appointed a professorship at the University of Bonn. He succeeded Rolf Huisgen as head of the organic chemistry department of the University of Munich in 1991. Wolfgang Steglich retired in 2001. Work The use of 4-dimethylaminopyridine for esterifications with anhydrides, which is sometimes called the Steglich esterification The Steglich esterific ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dichloromethane
Dichloromethane (DCM or methylene chloride, methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odour is widely used as a solvent. Although it is not miscible with water, it is slightly polar, and miscible with many organic solvents.Rossberg, M. ''et al.'' (2006) "Chlorinated Hydrocarbons" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim. . Occurrence Natural sources of dichloromethane include oceanic sources, macroalgae, wetlands, and volcanoes. However, the majority of dichloromethane in the environment is the result of industrial emissions. Production DCM is produced by treating either chloromethane or methane with chlorine gas at 400–500 °C. At these temperatures, both methane and chloromethane undergo a series of reactions producing progressively more chlorinated products. In this way, an estimated 400,000 tons were produced in the US, Europe, and Japan in 1993. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acylurea
Acylureas (also called ''N''-acylureas or ureides) are a class of chemical compounds formally derived from the acylation of urea. Uses Insecticides A subclass of acylureas known as benzoylureas are insecticides. They act as insect growth regulators by inhibiting the synthesis of chitin resulting in weakened cuticles and preventing molting. Members of this class include diflubenzuron, flufenoxuron, hexaflumuron, lufenuron, and teflubenzuron. Anticonvulsants and sedatives The acylurea functional group is also found in some pharmaceutical drugs such as the anticonvulsants phenacemide, pheneturide, chlorphenacemide, and acetylpheneturide (which are phenylureides), and the sedatives acecarbromal, bromisoval, and carbromal (which are bromoureides). Others include apronal (apronalide), capuride, and ectylurea. Barbiturates (a class of cyclic ureas) are structurally and mechanistically related to them. The phenylureides are also closely related to the hydantoins, such as phenytoin, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleophilic
In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are Lewis bases. ''Nucleophilic'' describes the affinity of a nucleophile to bond with positively charged atomic nuclei. Nucleophilicity, sometimes referred to as nucleophile strength, refers to a substance's nucleophilic character and is often used to compare the affinity of atoms. Neutral nucleophilic reactions with solvents such as alcohols and water are named solvolysis. Nucleophiles may take part in nucleophilic substitution, whereby a nucleophile becomes attracted to a full or partial positive charge, and nucleophilic addition. Nucleophilicity is closely related to basicity. History The terms ''nucleophile'' and ''electrophile'' were introduced by Christopher Kelk Ingold in 1933, replacing the terms ''anionoid'' and ''cationoid' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amine
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group (these may respectively be called alkylamines and arylamines; amines in which both types of substituent are attached to one nitrogen atom may be called alkylarylamines). Important amines include amino acids, biogenic amines, trimethylamine, and aniline; Inorganic derivatives of ammonia are also called amines, such as monochloramine (). The substituent is called an amino group. Compounds with a nitrogen atom attached to a carbonyl group, thus having the structure , are called amides and have different chemical properties from amines. Classification of amines Amines can be classified according to the nature and number of substituents on nitrogen. Aliphatic amines contain only H and alkyl substituents. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reaction Mechanism
In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs. A chemical mechanism is a theoretical conjecture that tries to describe in detail what takes place at each stage of an overall chemical reaction. The detailed steps of a reaction are not observable in most cases. The conjectured mechanism is chosen because it is thermodynamically feasible, and has experimental support in isolated intermediates (see next section) or other quantitative and qualitative characteristics of the reaction. It also describes each reactive intermediate, activated complex, and transition state, and which bonds are broken (and in what order), and which bonds are formed (and in what order). A complete mechanism must also explain the reason for the reactants and catalyst used, the stereochemistry observed in reactants and products, all products formed and the amount of each. The electron or arrow pushing method is often used in i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dicyclohexylurea
Dicyclohexylurea is an organic compound, specifically, a urea. It is the byproduct of the reaction of dicyclohexylcarbodiimide with amines or alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...s. It may be prepared by the reaction of cyclohexylamine and ''S'',''S''-dimethyl dithiocarbonate. 1,3-Dicyclohexyl urea (DCU) is a potent soluble epoxide hydrolase (sEH) inhibitor. It has been shown to lower systemic blood pressure by 22 ± 4 mmHg in SHR.{{cite journal , doi = 10.1111/j.1742-7843.2008.00213.x , author = Sarbani Ghosh, Po-Chang Chiang, Jan L. Wahlstrom, Hideji Fujiwara, Jon G. Selbo andSteven L. Roberds , title = Oral Delivery of 1,3-Dicyclohexylurea Nanosuspension Enhances Exposure and Lowers Blood Pressure in Hypertensive Rats , year = 2008, journal = Basic & ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Urea
Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important role in the metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals. It is a colorless, odorless solid, highly soluble in water, and practically non-toxic ( is 15 g/kg for rats). Dissolved in water, it is neither acidic nor alkaline. The body uses it in many processes, most notably nitrogen excretion. The liver forms it by combining two ammonia molecules () with a carbon dioxide () molecule in the urea cycle. Urea is widely used in fertilizers as a source of nitrogen (N) and is an important raw material for the chemical industry. In 1828 Friedrich Wöhler discovered that urea can be produced from inorganic starting materials, which was an important conceptual milestone ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solvent
A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for polar molecules and the most common solvent used by living things; all the ions and proteins in a cell are dissolved in water within the cell. The quantity of solute that can dissolve in a specific volume of solvent varies with temperature. Major uses of solvents are in paints, paint removers, inks, and dry cleaning. Specific uses for organic solvents are in dry cleaning (e.g. tetrachloroethylene); as paint thinners (toluene, turpentine); as nail polish removers and solvents of glue (acetone, methyl acetate, ethyl acetate); in spot removers (hexane, petrol ether); in detergents ( citrus terpenes); and in perfumes (ethanol). Solvents find various applications in chemical, pharmaceutical, oil, and gas industries, including in chemical syn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Esterification
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides are fatty acid esters of glycerol; they are important in biology, being one of the main classes of lipids and comprising the bulk of animal fats and vegetable oils. Esters typically have a pleasant smell; those of low molecular weight are commonly used as fragrances and are found in essential oils and pheromones. They perform as high-grade solvents for a broad array of plastics, plasticizers, resins, and lacquers, and are one of the largest classes of synthetic lubricants on the commercial market. Polyesters are important plastics, with monomers linked by ester moieties. Phosphoesters form the backbone of DNA molecules. Nitrate esters, such as nitroglycerin, are known for their explosive properties. '' Nomenclature Etymology The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
