|
Kowalski Ester Homologation
The Kowalski ester homologation is a chemical reaction for the homologation of esters. This reaction was designed as a safer alternative to the Arndt–Eistert synthesis, avoiding the need for diazomethane. The Kowalski reaction is named after its inventor, Conrad J. Kowalski. Reaction mechanism The mechanism is disputed. Variations By changing the reagent in the second step of the reaction, the Kowalski ester homologation can also be used for the preparation of silyl ynol ethers. See also * Curtius rearrangement The Curtius rearrangement (or Curtius reaction or Curtius degradation), first defined by Theodor Curtius in 1885, is the thermal decomposition of an acyl azide to an isocyanate with loss of nitrogen gas. The isocyanate then undergoes attack by a va ... References {{Reflist Rearrangement reactions Carbon-carbon bond forming reactions Name reactions Homologation reactions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Reaction
A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the Atomic nucleus, nuclei (no change to the elements present), and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive Chemical element, elements where both electronic and nuclear changes can occur. The substance (or substances) initially involved in a chemical reaction are called reagent, reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more Product (chemistry), products, which usually have properties different from the reactants. Reactions often consist of a sequence o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homologation Reaction
In organic chemistry, a homologation reaction, also known as homologization, is any chemical reaction that converts the reactant into the next member of the homologous series. A homologous series is a group of compounds that differ by a constant unit, generally a methylene () group. The reactants undergo a homologation when the number of a repeated structural unit in the molecules is increased. The most common homologation reactions increase the number of methylene () units in saturated chain within the molecule. For example, the reaction of aldehydes or ketones with diazomethane or methoxymethylenetriphenylphosphine to give the next homologue in the series. Examples of homologation reactions include: * Kiliani-Fischer synthesis, where an aldose molecule is elongated through a three-step process consisting of: *# Nucleophillic addition of cyanide to the carbonyl to form a cyanohydrin *# Hydrolysis to form a lactone *# Reduction to form the homologous aldose * Wittig reacti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ester
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 Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kowalski Ester Homologation Scheme
Kowalski (; feminine: Kowalska, plural: Kowalscy) is the second most common surname in Poland (140,471 people in 2009). ''Kowalski'' surname is derived from the word ''kowal'', meaning " lackmith". " Jan Kowalski" is a name that is used as a placeholder name in Poland in the meaning of " Average Joe", similar to "John Smith", its rough English-language equivalent, in English-speaking countries. (though a more direct translation would be "John Smithson"). Notable people * Alexander Kowalski (1902–1940), Polish ice hockey player killed in the Katyn massacre * Aleksander Kowalski (1930–2009), Polish Nordic combined skier * Alexander Kowalski (musician) (born 1978), German DJ, electronic music artist * Alfred Kowalski-Wierusz (1849–1915), Polish painter * Aneta Kowalska (born 1982), Polish pair skater * Annette Kowalski (born 1936), American producer, business partner of Bob Ross * Bernard Louis Kowalski (1929–2007), American director * Bronisława Kowalska (1955–202 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diazomethane
Diazomethane is the chemical compound CH2N2, discovered by German chemist Hans von Pechmann in 1894. It is the simplest diazo compound. In the pure form at room temperature, it is an extremely sensitive explosive yellow gas; thus, it is almost universally used as a solution in diethyl ether. The compound is a popular methylating agent in the laboratory, but it is too hazardous to be employed on an industrial scale without special precautions. Use of diazomethane has been significantly reduced by the introduction of the safer and equivalent reagent trimethylsilyldiazomethane. Use For safety and convenience diazomethane is always prepared as needed as a solution in ether and used as such. It converts carboxylic acids to methyl esters and phenols into their methyl ethers. The reaction is thought to proceed via proton transfer from carboxylic acid to diazomethane to give methyldiazonium cation, which reacts with the carboxylate ion to give the methyl ester and nitrogen gas. Label ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conrad J
Conrad may refer to: People * Conrad (name) Places United States * Conrad, Illinois, an unincorporated community * Conrad, Indiana, an unincorporated community * Conrad, Iowa, a city * Conrad, Montana, a city * Conrad Glacier, Washington Elsewhere * Conrad, Alberta, Canada, a former unincorporated community * Conrad Mountains, Queen Maud Land, Antarctica * Mount Conrad, Oates Land, Antarctica Businesses * Conrad Editora, a Brazilian publisher * Conrad Electronic, a German retailer * Conrad Hotels, the global luxury brand of Hilton Hotels * Conrad Models, a German manufacturer of diecast toys and promotional models Other uses * ''Conrad'' (comic strip) * CONRAD (organization), an American organization which promotes reproductive health in the developing world * ORP ''Conrad'', name of the cruiser HMS ''Danae'' (D44) while loaned to the Polish Navy (1944-1946) See also * Conradi * Conradin * Conradines * Conrads (other) * Corrado (other) * C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reagent
In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a substance ''consumed'' in the course of a chemical reaction. ''Solvents'', though involved in the reaction mechanism, are usually not called reactants. Similarly, ''catalysts'' are not consumed by the reaction, so they are not reactants. In biochemistry, especially in connection with enzyme-catalyzed reactions, the reactants are commonly called substrates. Definitions Organic chemistry In organic chemistry, the term "reagent" denotes a chemical ingredient (a compound or mixture, typically of inorganic or small organic molecules) introduced to cause the desired transformation of an organic substance. Examples include the Collins reagent, Fenton's reagent, and Grignard reagents. Analytical chemistry In analytical chemistry, a reagent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silyl
Silylation is the introduction of one or more (usually) substituted silyl groups (R3Si) to a molecule. The process is the basis of organosilicon chemistry. Of organic compounds Alcohols, carboxylic acids, amines, thiols, and phosphates can be silylated. The process involves the replacement of a proton with a trialkylsilyl group, typically trimethylsilyl (-SiMe3). Generally the substrate is deprotonated with a suitable strong base followed by treatment with a silyl chloride (e.g. trimethylsilyl chloride). Often strong bases such butyl lithium or a Grignard reagent are used, as illustrated by the synthesis of a trimethylsilyl ethers as protecting groups from an alcohol: :ROH + BuLi → ROLi + BuH :ROLi + Me3SiCl → ROSiMe3 + LiCl Bis(trimethylsilyl)acetamide ("BSA", Me3SiNC(OSiMe3)Me is an efficient silylation agent used for the derivatisation of compounds. The reaction of BSA with alcohols gives the corresponding trimethylsilyl ether, together with N-(trimethylsilyl)acetamide as a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ynol
In organic chemistry, an alkynol (shortened to ynol) is an alkyne with a hydroxyl group affixed to one of the two carbon atoms composing the triple bond (). The deprotonated anions of ynols are known as ''ynolates''. An ynol with hydroxyl groups on both sides of its triple bond is known as an ynediol; only one ynediol, acetylenediol, exists. Ynolates Ynolates are chemical compounds with a negatively charged oxygen atom attached to an alkyne functionality. They were first synthesized in 1975 by Schöllkopf and Hoppe via the ''n''-butyllithium fragmentation of 3,4-diphenylisoxazole. Synthetically, they behave as ketene precursors or synthons. Ynol–ketene tautomerism Ynols can interconvert with ketenes, much like enols can with aldehydes and ketones. The ynol tautomer is usually unstable, does not survive long, and changes into the ketene. This is because oxygen is more electronegative than carbon and thus forms stronger bonds. For instance, ethynol quickly inter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ether
In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be classified into two varieties: if the alkyl or aryl groups are the same on both sides of the oxygen atom, then it is a simple or symmetrical ether, whereas if they are different, the ethers are called mixed or unsymmetrical ethers. A typical example of the first group is the solvent and anaesthetic diethyl ether, commonly referred to simply as "ether" (). Ethers are common in organic chemistry and even more prevalent in biochemistry, as they are common linkages in carbohydrates and lignin. Structure and bonding Ethers feature bent C–O–C linkages. In dimethyl ether, the bond angle is 111° and C–O distances are 141 pm. The barrier to rotation about the C–O bonds is low. The bonding of oxygen in ethers, alcohols, and water is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
acetamide.svg "Click for more on -> Silyl")
.svg "Click for more on -> Ether")