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Knorr Pyrrole Synthesis
The Knorr pyrrole synthesis is a widely used chemical reaction that synthesizes substituted pyrroles (3). The method involves the reaction of an α-amino-ketone (1) and a compound containing an electron-withdrawing group (e.g. an ester as shown) α to a carbonyl group (2). Method The mechanism requires zinc and acetic acid as catalysts. It will proceed at room temperature. Because α-amino-ketones self-condense very easily, they must be prepared ''in situ''. The usual way of doing this is from the relevant oxime, via the Neber rearrangement. The original Knorr synthesis employed two equivalents of ethyl acetoacetate, one of which was converted to ethyl 2-oximinoacetoacetate by dissolving it in glacial acetic acid, and slowly adding one equivalent of saturated aqueous sodium nitrite, under external cooling. Zinc dust was then stirred in, reducing the oxime group to the amine. This reduction consumes two equivalents of zinc and four equivalents of acetic acid. Modern practice i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ludwig Knorr
Ludwig Knorr (2 December 1859 – 4 June 1921) was a German chemist. Together with Carl Paal, he discovered the Paal–Knorr synthesis, and the Knorr quinoline synthesis and Knorr pyrrole synthesis are also named after him. The synthesis in 1883 of the analgesic drug antipyrine, now called phenazone, was a commercial success. Antipyrine was the first synthetic drug and the most widely used drug until it was replaced by Aspirin in the early 20th century. Early life Ludwig Knorr was born to a wealthy merchant family in 1859. He grew up in the Sabbadini-Knorr company headquarters, located in the Kaufingerstraße in the center of Munich, and in the family house near the Lake Starnberg. After the early death of his father, the education of him and his four brothers lay in the hands of their mother. In 1878 Knorr received his Abitur and started to study chemistry at the University of Munich. In the beginning, he studied under Jacob Volhard; then, after Volhard left for the Universi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exothermic
In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e.g. a battery), or sound (e.g. explosion heard when burning hydrogen). The term ''exothermic'' was first coined by 19th-century French chemist Marcellin Berthelot. The opposite of an exothermic process is an endothermic process, one that absorbs energy usually in the form of heat. The concept is frequently applied in the physical sciences to chemical reactions where chemical bond energy is converted to thermal energy (heat). Two types of chemical reactions Exothermic and endothermic describe two types of chemical reactions or systems found in nature, as follows: Exothermic After an exothermic reaction, more energy has been released to the surroundings than was absorbed to initiate and maintain the reaction. An example would be the burn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Journal Of Organic Chemistry
''The Journal of Organic Chemistry'', colloquially known as ''JOC'', is a peer-reviewed scientific journal for original contributions of fundamental research in all branches of theory and practice in organic and bioorganic chemistry. It is published by the publishing arm of the American Chemical Society, with 24 issues per year. According to the ''Journal Citation Reports'', the journal had a 2017 impact factor of 4.805 and it is the journal that received the most cites (100,091 in 2017) in the field of organic chemistry. According to Web of Knowledge (and as December 2012), eleven papers from the journal have received more than 1,000 citations, with the most cited paper having received 7,967 citations. The current editor-in-chief is Scott J. Miller from Yale University. Indexing ''J. Org. Chem.'' is currently indexed in: See also *Organic Letters *Organometallics ''Organometallics'' is a biweekly journal published by the American Chemical Society. Its area of focus is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tert-butyl Alcohol
''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] |
Meldrum's Acid
Meldrum's acid or 2,2-dimethyl-1,3-dioxane-4,6-dione is an organic compound with formula . Its molecule has a heterocyclic core with four carbon and two oxygen atoms; the formula can also be written as . It is a crystalline colorless solid, sparingly soluble in water. It decomposes on heating with release of carbon dioxide and acetone. Properties Acidity The compound can easily lose a hydrogen ion from the methylene element in the ring (carbon 5); which creates a double bond between it and one of the adjacent carbons (number 4 or 6), and a negative charge in the corresponding oxygen. The resulting anion is stabilized by resonance between the two alternatives, so that the double bond is delocalized and each oxygen in the carbonyls has a formal charge of −1/2. The ionization constant p''K''a is 4.97; which makes it behave as a monobasic acid even though it contains no carboxylic acid groups. In this and other properties, the compound resembles dimedone and barbituric ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acid Chloride
In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group . Their formula is usually written , where R is a side chain. They are reactive derivatives of carboxylic acids (). A specific example of an acyl chloride is acetyl chloride, . Acyl chlorides are the most important subset of acyl halides. Nomenclature Where the acyl chloride moiety takes priority, acyl chlorides are named by taking the name of the parent carboxylic acid, and substituting ''-yl chloride'' for ''-ic acid''. Thus: : : When other functional groups take priority, acyl chlorides are considered prefixes — ''chlorocarbonyl-'': : Properties Lacking the ability to form hydrogen bonds, acyl chlorides have lower boiling and melting points than similar carboxylic acids. For example, acetic acid boils at 118 °C, whereas acetyl chloride boils at 51 °C. Like most carbonyl compounds, infrared spectroscopy reveals a band near 1750 cm−1. The simplest s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trifluoroacetic Acid
Trifluoroacetic acid (TFA) is an organofluorine compound with the chemical formula CF3CO2H. It is a structural analogue of acetic acid with all three of the acetyl group's hydrogen atoms replaced by fluorine atoms and is a colorless liquid with a vinegar-like odor. TFA is a stronger acid than acetic acid, having an acid ionisation constant, ''K''a, that is approximately 34,000 times higher, as the highly electronegative fluorine atoms and consequent electron-withdrawing nature of the trifluoromethyl group weakens the oxygen-hydrogen bond (allowing for greater acidity) and stabilises the anionic conjugate base. TFA is widely used in organic chemistry for various purposes. Synthesis TFA is prepared industrially by the electrofluorination of acetyl chloride or acetic anhydride, followed by hydrolysis of the resulting trifluoroacetyl fluoride: : + 4 → + 3 + : + → + Where desired, this compound may be dried by addition of trifluoroacetic anhydride. An older route to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palladium On Carbon
Palladium on carbon, often referred to as Pd/C, is a form of palladium used as a catalyst. The metal is supported on activated carbon to maximize its surface area and activity. Uses Hydrogenation Palladium on carbon is used for catalytic hydrogenations in organic synthesis. Examples include reductive amination, carbonyl reduction, nitro compound reduction, the reduction of imines and Schiff bases and debenzylation reactions. Hydrogenolysis Palladium on carbon is a common catalyst for hydrogenolysis. Such reactions are helpful in deprotection strategies. Particularly common substrate for hydrogenolysis are benzyl ethers: *: Other labile substituents are also susceptible to cleavage by this reagent. Coupling reactions Palladium on carbon is also used for coupling reactions. Examples include the Suzuki reaction and Stille reaction. Preparation A solution of palladium chloride and hydrochloric acid is combined with aqueous suspension of activated carbon. The palladium(II) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogenolysis
Hydrogenolysis is a chemical reaction whereby a carbon–carbon or carbon–heteroatom single bond is cleaved or undergoes lysis (breakdown) by hydrogen.Ralph Connor, Homer Adkins. Hydrogenolysis Of Oxygenated Organic Compounds. J. Am. Chem. Soc.; 1932; 54(12); 4678–4690. The heteroatom may vary, but it usually is oxygen, nitrogen, or sulfur. A related reaction is hydrogenation, where hydrogen is added to the molecule, without cleaving bonds. Usually hydrogenolysis is conducted catalytically using hydrogen gas. History The term "hydrogenolysis" was coined by Carleton Ellis in reference to hydrogenolysis of carbon–carbon bonds. Earlier, Paul Sabatier had already observed the hydrogenolysis of benzyl alcohol to toluene, and as early as 1906, Padoa and Ponti had observed the hydrogenolysis of furfuryl alcohol. Homer Burton Adkins and Ralph Connor were the first to call the carbon–oxygen bond cleavage "hydrogenolysis". In the petrochemical industry In petroleum refineries, c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tert-butyl
In organic chemistry, butyl is a four-carbon alkyl radical or substituent group with general chemical formula , derived from either of the two isomers (''n''-butane and isobutane) of butane. The isomer ''n''-butane can connect in two ways, giving rise to two "-butyl" groups: * If it connects at one of the two terminal carbon atoms, it is normal butyl or ''n''-butyl: (preferred IUPAC name: butyl) * If it connects at one of the non-terminal (internal) carbon atoms, it is secondary butyl or ''sec''-butyl: (preferred IUPAC name: butan-2-yl) The second isomer of butane, isobutane, can also connect in two ways, giving rise to two additional groups: * If it connects at one of the three terminal carbons, it is isobutyl: (preferred IUPAC name: 2-methylpropyl) * If it connects at the central carbon, it is tertiary butyl, ''tert''-butyl or ''t''-butyl: (preferred IUPAC name: ''tert''-butyl) Nomenclature According to IUPAC nomenclature, "isobutyl", "''sec''-butyl", and "''tert''-b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzyl
In organic chemistry, benzyl is the substituent or molecular fragment possessing the structure . Benzyl features a benzene ring () attached to a methylene group () group. Nomenclature In IUPAC nomenclature, the prefix benzyl refers to a substituent, for example benzyl chloride or benzyl benzoate. Benzyl is not to be confused with phenyl with the formula . The term benzylic is used to describe the position of the first carbon bonded to a benzene or other aromatic ring. For example, is referred to as a "benzylic" carbocation. The benzyl free radical has the formula . The benzyl cation or phenylcarbenium ion is the carbocation with formula ; the benzyl anion or phenylmethanide ion is the carbanion with the formula . None of these species can be formed in significant amounts in the solution phase under normal conditions, but they are useful referents for discussion of reaction mechanisms and may exist as reactive intermediates. Abbreviations The abbreviation "Bn" denotes benzyl. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of The American Chemical Society
The ''Journal of the American Chemical Society'' is a weekly peer-reviewed scientific journal that was established in 1879 by the American Chemical Society. The journal has absorbed two other publications in its history, the ''Journal of Analytical and Applied Chemistry'' (July 1893) and the ''American Chemical Journal'' (January 1914). It covers all fields of chemistry. Since 2021, the editor-in-chief is Erick M. Carreira (ETH Zurich). In 2014, the journal moved to a hybrid open access publishing model. Abstracting and indexing The journal is abstracted and indexed in Chemical Abstracts Service, Scopus, EBSCO databases, ProQuest databases, Index Medicus/MEDLINE/PubMed, and the Science Citation Index Expanded. According to the ''Journal Citation Reports'', the journal has a 2021 impact factor of 16.383. Editors-in-chief The following people are or have been editor-in-chief: * 1879–1880 – Hermann Endemann * 1880–1881 – Gideon E. Moore * 1881–1882 – Hermann Endemann ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
