|
Eschweiler–Clarke Reaction
The Eschweiler–Clarke reaction (also called the Eschweiler–Clarke methylation) is a chemical reaction whereby a primary (or secondary) amine is methylated using excess formic acid and formaldehyde. Reductive amination reactions such as this one will not produce quaternary ammonium salts, but instead will stop at the tertiary amine stage. It is named for the German chemist Wilhelm Eschweiler (1860–1936) and the British chemist Hans Thacher Clarke (1887-1972). Mechanism The reaction is generally performed in an aqueous solution at close to boiling. The first methylation of the amine begins with imine formation with formaldehyde. The formic acid acts as a source of hydride and reduces the imine to a secondary amine. Loss of carbon dioxide gas renders the reaction irreversible. Despite being more hindered, the formation of the tertiary amine is more favorable, as the intermediate in iminium ion is formed without needing to protonate. Hence the treatment of a primary amine wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hans Thacher Clarke
Hans Thacher Clarke (27 December 1887 – 21 October 1972) was a prominent biochemist during the first half of the twentieth century. He was born in England where he received his university training, but also studied in Germany and Ireland. He spent the remainder of his life in the United States. Biography Clarke was born in Harrow in England. His father was Joseph Thacher Clarke, an archeologist. His older sister was the composer and violist Rebecca Clarke. Hans Clarke attended University College London School, and went on to enter the University as a student of chemistry, where he studied under William Ramsay, J. Norman Collie, and Samuel Smiles. He received a degree (Bachelor of Science) in 1908, and continued performing research at the University directed by Smiles and Stewart. In 1911 he was awarded an 1851 Exhibition Scholarship, which allowed him to study for three semesters in Berlin under Emil Fischer, and one semester with A. W. Stewart at Queen's College, Belfast. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Imine
In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bonds. Imines are common in synthetic and naturally occurring compounds and they participate in many reactions. Structure For ketimines and aldimines, respectively, the five core atoms (C2C=NX and C(H)C=NX, X = H or C) are coplanar. Planarity results from the sp2-hybridization of the mutually double-bonded carbon and the nitrogen atoms. The C=N distance is 1.29-1.31 Å for nonconjugated imines and 1.35 Å for conjugated imines. By contrast, C-N distances in amines and nitriles are 1.47 and 1.16 Å, respectively. Rotation about the C=N bond is slow. Using NMR spectroscopy, both E- and Z-isomers of aldimines have been detected. Owing to steric effects, the E isomer is favored. Nomenclature and classification The term "imine" was coine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Redox Reactions
Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or is the product of decay, or is composed of organic compounds * Organic compound, a compound that contains carbon ** Organic chemistry, chemistry involving organic compounds Farming, certification and products * Organic farming, agriculture conducted according to certain standards, especially the use of stated methods of fertilization and pest control * Organic certification, accreditation process for producers of organically-farmed products * Organic horticulture, the science and art of growing fruits, vegetables, flowers, or ornamental plants by following the essential principles of organic agriculture * Organic products, "organics": ** Organic food, food produced from organic farming methods and often certified organic according to organic farming stand ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leuckart–Wallach Reaction
The Leuckart reaction is the chemical reaction that converts aldehydes or ketones to amines by reductive amination in the presence of heat. The reaction, named after Rudolf Leuckart, uses either ammonium formate or formamide as the nitrogen donor and reducing agent. It requires high temperatures, usually between 120 and 130 °C; for the formamide variant, the temperature can be greater than 165 °C. History The Leuckart reaction is named in honor of its developer, the German chemist Rudolf Leuckart (1854–1899). He discovered that heating benzaldehyde with formamide does not produce benzylidenediformamide as anticipated, but benzylamine. In 1891, a colleague of Leuckart at the University of Göttingen, Otto Wallach, performed further reactions using alicyclic and terpenoid ketones as well as aldehydes, demonstrating the general application. Over the course of the past century, chemists have discovered several methods to improve the yield of the reaction and carry i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Cyanoborohydride
Sodium cyanoborohydride is the chemical compound with the formula Sodium, NaBoron, BHydrogen, H3cyanide, CN. It is a colourless salt, but commercial samples can appear tan. It is widely used in organic synthesis for the reduction of imines. The salt tolerates aqueous conditions. Use Owing to the presence of the electron-withdrawing cyanide substituent, [B(CN)H3]− is less reducing than is sodium borohydride, [BH4]−. As a mild reducing agent, it is used to convert imines to amines. It is especially favored for reductive aminations, wherein aldehydes or ketones are treated with an amine in the presence of this reagent: : R2CO + R'NH2 + NaBH3CN + CH3OH → R2CH-NHR' + "NaCH3OBH2CN" The reagent is typically used in excess. Selectivity is achieved at mildly basic solutions (pH 7–10). The reagent is ideal for reductive aminations ("Borch Reaction"). In conjunction with tosylhydrazine, sodium cyanoborohydride is used in the reductive deoxygenation of ketones. Structure and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon Dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transparent to visible light but absorbs infrared radiation, acting as a greenhouse gas. It is a trace gas in Earth's atmosphere at 421 parts per million (ppm), or about 0.04% by volume (as of May 2022), having risen from pre-industrial levels of 280 ppm. Burning fossil fuels is the primary cause of these increased CO2 concentrations and also the primary cause of climate change.IPCC (2022Summary for policy makersiClimate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA Carbon dioxide is soluble in water and is found in groundwater, lakes, ice caps, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Redox
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state. There are two classes of redox reactions: * ''Electron-transfer'' – Only one (usually) electron flows from the reducing agent to the oxidant. This type of redox reaction is often discussed in terms of redox couples and electrode potentials. * ''Atom transfer'' – An atom transfers from one substrate to another. For example, in the rusting of iron, the oxidation state of iron atoms increases as the iron converts to an oxide, and simultaneously the oxidation state of oxygen decreases as it accepts electrons released by the iron. Although oxidation reactions are commonly associated with the formation of oxides, other chemical species can serve the same function. In hydrogen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydride
In chemistry, a hydride is formally the anion of hydrogen( H−). The term is applied loosely. At one extreme, all compounds containing covalently bound H atoms are called hydrides: water (H2O) is a hydride of oxygen, ammonia is a hydride of nitrogen, etc. For inorganic chemists, hydrides refer to compounds and ions in which hydrogen is covalently attached to a less electronegative element. In such cases, the H centre has nucleophilic character, which contrasts with the protic character of acids. The hydride anion is very rarely observed. Almost all of the elements form binary compounds with hydrogen, the exceptions being He, Ne, Ar, Kr, Pm, Os, Ir, Rn, Fr, and Ra. Exotic molecules such as positronium hydride have also been made. Bonds Bonds between hydrogen and the other elements range from highly to somewhat covalent. Some hydrides, e.g. boron hydrides, do not conform to classical electron-counting rules and the bonding is described in terms of multi-centered ... [...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] |
Chemische Berichte
''Chemische Berichte'' (usually abbreviated as ''Ber.'' or ''Chem. Ber.'') was a German-language scientific journal of all disciplines of chemistry founded in 1868. It was one of the oldest scientific journals in chemistry, until it merged with ''Recueil des Travaux Chimiques des Pays-Bas'' to form ''Chemische Berichte/Recueil'' in 1997. ''Chemische Berichte/Recueil'' was then merged with other European journals in 1998 to form ''European Journal of Inorganic Chemistry''. History Founded in 1868 as ''Berichte der Deutschen Chemischen Gesellschaft'' (, CODEN BDCGAS), it operated under this title until 1928 (Vol. 61). The journal was then split into: * ''Berichte der Deutschen Chemischen Gesellschaft, A: Vereins-Nachrichten'' (, CODEN BDCAAS), and * ''Berichte der Deutschen Chemischen Gesellschaft, B: Abhandlungen'' (, CODEN BDCBAD). Vol. 78 and 79 (1945–1946) were omitted and not published due to World War II. The journal was renamed ''Chemische Berichte'' (, CODEN CHBEAM) in 19 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
