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Kowalski Ester Homologation
The Kowalski ester homologation is a chemical reaction for the homologation reaction, 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 References {{Reflist Rearrangement reactions Homologation reactions Carbon-carbon bond forming reactions Name reactions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Reaction
A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, energy change as new products are generated. 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 (c ... [...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 reac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ester
In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distinctive functional group. Analogues derived from oxygen replaced by other chalcogens belong to the ester category as well. According to some authors, organyl derivatives of acidic hydrogen of other acids are esters as well (e.g. amides), but not according to the IUPAC. 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. Lactones are cyclic carboxylic esters; naturally occurring lactones are mainly 5- and 6-membered ring lactones. Lactones contribute to the aroma of fruits, butter, cheese, vegetables like celery and other foods. Esters can be formed from oxoacids (e.g. esters of acetic acid, carbonic acid ... [...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 used as a placeholder name in Poland to mean " John Smith", much as "John Doe" is used in English-speaking countries. 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 (1849–1915), Polish painter * Annette Kowalski (born 1936), American producer, business partner of Bob Ross * Bernard Louis Kowalski (1929–2007), American director * Bronisława Kowalska (1955–2020), Polish politician * Chana Kowalska (1899-1942), Polish Jewish painter and journalist * Craig Kowalski (born 1981), American ice hockey player * Daniel Kowalski (born 1975), Australi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diazomethane
Diazomethane is an organic chemical compound with the formula 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 diethyl ether, 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 a methyldiazonium cation, which reacts with the carboxylate ion to give th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conrad J
Conrad may refer to: People * Conrad (name) * Saint Conrad (other) Places United States * Conrad, Illinois, 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 * Mount Conrad (Canada), Purcell Mountains, British Columbia 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'' (comic strip) * CONRAD (organization), an American organization that promotes reproductive health in the developing world * ORP ''Conrad'', name of the cruiser HMS Danae (D44), HMS ''Danae'' (D44) while loaned to the Polish Navy (1944-1946) See also * Conrad ... [...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 reag ... [...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. Silylations are core methods for production of organosilicon chemistry. Silanization, while similar to silylation, usually refers to attachment of silyl groups to solids. Silyl groups are commonly used for: alcohol protection, enolate trapping, gas chromatography, electron-impact mass spectrometry (EI-MS), and coordinating with metal complexes. Protection Chemistry Protection Silylation is often used to protect alcohols, as well as amines, carboxylic acids, and terminal alkynes. The products after silylation, namely silyl ethers and silyl amines, are resilient toward basic conditions. Protection is typically done by reacting the functional group with a silyl halide by an SN2 reaction mechanism, typically in the presence of base. The protection mechanism begins with the base deprotonating the alcohol group. Next, the deprotonated alcohol group attacks the silyl atom of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ynol
In organic chemistry, alkynols (''hydroxyalkynes'') are organic compounds that contain both alkyne and alcohol functional groups. Thus, as structural features, they have a C≡C triple bond and a hydroxyl group. Some alkynols play a role as intermediates in the chemical industry. The shortened term ynol typically refers to alkynols with the hydroxyl group affixed to one of the two carbon atoms composing the triple bond (), the triple-bond analogues to enols. Ynols can tautomerize to ketenes. The deprotonated anions of ynols are known as ynolates, the triple-bond analogues to enolates. Synthesis Alkynols may be formed by the alkynylation of carbonyl compounds, usually in liquid ammonia. 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 pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ether
In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R′ represent the organyl groups. Ethers can again be classified into two varieties: if the organyl 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 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 ox ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
