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Wolff–Kishner Reduction
The Wolff–Kishner reduction is a reaction used in organic chemistry to convert carbonyl functionalities into methylene groups. In the context of complex molecule synthesis, it is most frequently employed to remove a carbonyl group after it has served its synthetic purpose of activating an intermediate in a preceding step. As such, there is no obvious retron for this reaction. The reaction was reported by Nikolai Kischner in 1911 and Ludwig Wolff in 1912, In general, the reaction mechanism first involves the ''in situ'' generation of a hydrazone by condensation of hydrazine with the ketone or aldehyde substrate. Sometimes it is however advantageous to use a pre-formed hydrazone as substrate (see modifications). The rate determining step of the reaction is de-protonation of the hydrazone by an alkoxide base to form a diimide anion by a concerted, solvent mediated protonation/de-protonation step. Collapse of this alkyldiimide with loss of N2 leads to formation of an alkylanion whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ludwig Wolff
Ludwig Wolff (27 September 1857 – 24 February 1919), born in Neustadt in Palatinate (region), Palatinate, was a German chemist. He studied chemistry at the University of Strasbourg, where he received his Ph.D. from Rudolph Fittig in 1882. He became Professor of analytical chemistry at the University of Jena in 1891 and held this position till his death in 1919. In 1911 he published a new reaction now known as the Wolff-Kishner reduction. His name is also associated with the chemical reaction known as the Wolff rearrangement (1912). References 1857 births 1919 deaths 19th-century German chemists People from the Rhine Province University of Strasbourg alumni Academic staff of the University of Jena People from Neustadt an der Weinstraße 20th-century German chemists {{Germany-chemist-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rate-determining Step
In chemical kinetics, the overall rate of a reaction is often approximately determined by the slowest step, known as the rate-determining step (RDS or RD-step or r/d step) or rate-limiting step. For a given reaction mechanism, the prediction of the corresponding rate equation (for comparison with the experimental rate law) is often simplified by using this approximation of the rate-determining step. In principle, the time evolution of the reactant and product concentrations can be determined from the set of simultaneous rate equations for the individual steps of the mechanism, one for each step. However, the analytical solution of these differential equations is not always easy, and in some cases numerical integration may even be required. The hypothesis of a single rate-determining step can greatly simplify the mathematics. In the simplest case the initial step is the slowest, and the overall rate is just the rate of the first step. Also, the rate equations for mechanisms with a s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catecholborane
Catecholborane (abbreviated HBcat) is an organoboron compound that is useful in organic synthesis. This colourless liquid is a derivative of catechol and a borane, having the formula C6H4O2BH. Synthesis and structure Traditionally catecholborane is produced by treating catechol with borane (BH3) in a cooled solution of THF. However, this method results in a loss of 2 mole equivalents of the hydride. Nöth and Männig described the reaction of alkali-metal boron hydride (LiBH4, NaBH4, of KBH4) with tris(catecholato)bisborane in an ethereal solvent such as diethyl ether. In 2001, Herbert Brown and coworkers prepared catecholborane by treatment of tri-''o''-phenylene bis-borate with diborane. Unlike borane itself or alkylboranes, catechol borane exists as a monomer. This behavior is a consequence of the electronic influence of the aryloxy groups that diminish the Lewis acidity of the boron centre. Pinacolborane adopts a similar structure. Reactions Catecholborane is less reactive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Triacetoxyborohydride
Sodium triacetoxyborohydride, also known as sodium triacetoxyhydroborate, commonly abbreviated STAB, is a chemical compound with the formula Na(CH3COO)3BH. Like other borohydrides, it is used as a reducing agent in organic synthesis. This colourless salt is prepared by protonolysis of sodium borohydride with acetic acid: :NaBH4 + 3 HO2CCH3 → NaBH(O2CCH3)3 + 3 H2 Comparison with related reagents Sodium triacetoxyborohydride is a milder reducing agent than sodium borohydride or even sodium cyanoborohydride. It reduces aldehydes but not most ketones. It is especially suitable for reductive aminations of aldehydes and ketones. However, unlike sodium cyanoborohydride, the triacetoxyborohydride hydrolyzes readily, nor is it compatible with methanol. It reacts only slowly with ethanol and isopropanol and can be used with these. NaBH(OAc)3 may also be used for reductive alkylation of secondary amines with aldehyde-bisulfite adducts. Monoacetoxyborohydride The combination ... [...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] |
Tosylhydrazone
A tosylhydrazone in organic chemistry is a functional group with the general structure RR'C=N-NH-Ts where Ts is a tosyl group. Organic compounds having this functional group can be accessed by reaction of an aldehyde or ketone with tosylhydrazine. Synthesis As an example ''camphor tosylhydrazone'' is synthesised from camphor and tosylhydrazine in ethanol with hydrochloric acid catalysis. Reactions Hydrolysis is the reverse reaction of formation with regeneration of the carbonyl compound. In the Shapiro reaction tosylhydrazones are used as a leaving group in elimination reactions. This reaction requires a strong base. If sodium methoxide is used as the base the reaction is called a Bamford–Stevens reaction. Tosylhydrazones can be organic reduction, reduced to the corresponding alkanes with reagents such as sodium borohydride and borane. Tosylhydrazone salts can react with metals to form metal carbenes and used in cyclopropanations and epoxidations. An example of a transition me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cram Modification1
Cram may refer to: * Cram (surname), a surname, and list of notable persons having the surname * Cram.com, a website for creating and sharing flashcards * Cram (Australian game show), a television show * ''Cram'' (game show), a TV game show that aired on the Game Show Network * Cram (game), an impartial mathematical game similar to domineering * Cram (software), a flashcard application for Apple devices * Cram Motorsport, an auto racing team based in Italy CRAM may refer to: * NCR CRAM, Card Random-Access Memory, a computer memory technology developed by NCR * Chalcogenide RAM, Chalcogenide random access memory, a phase-change computer memory technology * Challenge–response authentication mechanism, a computer security procedure * Counter-RAM, Counter-Rockets, Artillery and Mortars, a weapons system * MS-CRAM, also known as Microsoft Video 1, a codec * CRAM diet, the Cereal, Rice, And Milk diet * CRAM (file format), a compressed genome sequence alignment file See also * Cramm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diethylene Glycol
Diethylene glycol (DEG) is an organic compound with the formula (HOCH2CH2)2O. It is a colorless, practically odorless, and hygroscopic liquid with a sweetish taste. It is a four carbon dimer of ethylene glycol. It is miscible in water, alcohol, ether, acetone, and ethylene glycol. DEG is a widely used solvent.Siegfried Rebsdat and Dieter Mayer "Ethylene Glycol" in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim.. It can be a contaminant in consumer products; this has resulted in numerous epidemics of poisoning since the early 20th century. Preparation DEG is produced by the partial hydrolysis of ethylene oxide. Depending on the conditions, varying amounts of DEG and related glycols are produced. The resulting product is two ethylene glycol molecules joined by an ether bond. "Diethylene glycol is derived as a co-product with ethylene glycol (MEG) and triethylene glycol. The industry generally operates to maximize MEG production. Ethylene glycol is by f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Huang-Minlon Modification
Huang Minlon, Huang-Minlon, or Huang Minglong (; 3 July 1898 – 1 July 1979) was a Chinese organic chemist and pharmaceutical scientist. Huang is considered a pioneer and founder of modern pharmaceutical industries in China. Life Huang was born in Yangzhou, Jiangsu Province on 3 July 1898, during the late Qing dynasty. In 1917, Huang graduated from Yangzhou Middle School. In 1918, Huang graduated from the Zhejiang Provincial College of Medicine (current Zhejiang University School of Medicine). In 1924, Huang obtained PhD from the University of Berlin, Germany. In 1925, Huang went back to China and became a professor and later department head at Zhejiang Provincial College of Medicine. From 1934 to 1940, Huang worked in research in Germany and the UK. Huang returned to China in 1940 and became a senior researcher at Academia Sinica. Huang was also a professor at the renowned wartime National Southwestern Associated University during the Japanese occupation. Subsequently, durin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Huang Minlon
Huang Minlon, Huang-Minlon, or Huang Minglong (; 3 July 1898 – 1 July 1979) was a Chinese organic chemist and pharmaceutical scientist. Huang is considered a pioneer and founder of modern pharmaceutical industries in China. Life Huang was born in Yangzhou, Jiangsu Province on 3 July 1898, during the late Qing dynasty. In 1917, Huang graduated from Yangzhou Middle School. In 1918, Huang graduated from the Zhejiang Provincial College of Medicine (current Zhejiang University School of Medicine). In 1924, Huang obtained PhD from the University of Berlin, Germany. In 1925, Huang went back to China and became a professor and later department head at Zhejiang Provincial College of Medicine. From 1934 to 1940, Huang worked in research in Germany and the UK. Huang returned to China in 1940 and became a senior researcher at Academia Sinica. Huang was also a professor at the renowned wartime National Southwestern Associated University during the Japanese occupation. Subsequently, duri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
