|
Neber Rearrangement
The Neber rearrangement is an organic reaction in which a ketoxime is converted into an alpha- aminoketone via a rearrangement reaction. : The oxime is first converted to an O-sulfonate, for example a tosylate by reaction with tosyl chloride. Added base forms a carbanion which displaces the tosylate group in a nucleophilic displacement to an azirine and added water subsequently hydrolyses it to the aminoketone. The Beckmann rearrangement is a side reaction A side reaction is a chemical reaction that occurs at the same time as the actual main reaction, but to a lesser extent. It leads to the formation of by-product, so that the yield of main product is reduced: : + B -> []_P2 P1_is_th_.... _References Rearrangement_reactions Name_reactions {{Chemistry-stub}.html" ;"title=" P1 : + C ->[] P2 P1 is th .... References Rearrangement reactions Name reactions {{Chemistry-stub}"> P1 : + C ->[] P2 P1 is th .... References Rearrangement reactions Name reactions {{Chemi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Reaction
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, Mechanistic Organic Photochemistry, photochemical reactions and organic redox reaction, redox reactions. In organic synthesis, organic reactions are used in the construction of new organic molecules. The production of many man-made chemicals such as drugs, plastics, food additives, fabrics depend on organic reactions. The oldest organic reactions are combustion of organic fuels and saponification of fats to make soap. Modern organic chemistry starts with the Wöhler synthesis in 1828. In the history of the Nobel Prize in Chemistry awards have been given for the invention of specific organic reactions such as the Grignard reaction in 1912, the Diels-Alder reaction in 1950, the Wittig reaction in 1979 and olefin metathesis in 2005. Classifications Organic c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ketoxime
In organic chemistry, an oxime is a organic compound belonging to the imines, with the general formula , where R is an organic side-chain and R’ may be hydrogen, forming an aldoxime, or another organic group, forming a ketoxime. O-substituted oximes form a closely related family of compounds. Amidoximes are oximes of amides () with general structure . Oximes are usually generated by the reaction of hydroxylamine with aldehydes () or ketones (). The term ''oxime'' dates back to the 19th century, a combination of the words ''oxygen'' and ''imine''. Structure and properties If the two side-chains on the central carbon are different from each other—either an aldoxime, or a ketoxime with two different "R" groups—the oxime can often have two different geometric stereoisomeric forms according to the ''E''/''Z'' configuration. An older terminology of ''syn'' and ''anti'' was used to identify especially aldoximes according to whether the R group was closer or further from th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aminoaldehydes And Aminoketones
Aminoaldehydes and aminoketones are organic compounds that contain an amine functional group as well as either a aldehyde or ketone functional group. These compounds are important in biology and in chemical synthesis. Because of their bifunctional nature, they have attracted much attention from chemists. Tertiary amine derivatives Because primary and secondary amines react with aldehydes and ketones, the most common variety of these aminocarbonyl compounds feature tertiary amines. Such compounds are produced by amination of α-haloketones and α- haloaldehydes. Examples include cathinones, methadone, molindone, pimeclone, ferruginine, and tropinone. Secondary amine derivatives Aminoketones containing secondary amines are typically stable when the ketone is located on a ring, e.g. 4-piperidinone, triacetonamine, acridone Primary amine derivatives Most members of this class are unstable towards self-condensation, however some important examples do exist as intermediates in bi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rearrangement Reaction
In organic chemistry, a rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. Often a substituent moves from one atom to another atom in the same molecule, hence these reactions are usually intramolecular. In the example below, the substituent R moves from carbon atom 1 to carbon atom 2: :\underset\ce\ce\underset\ce\ce Intermolecular rearrangements also take place. A rearrangement is not well represented by simple and discrete electron transfers (represented by curved arrows in organic chemistry texts). The actual mechanism of alkyl groups moving, as in Wagner-Meerwein rearrangement, probably involves transfer of the moving alkyl group fluidly along a bond, not ionic bond-breaking and forming. In pericyclic reactions, explanation by orbital interactions give a better picture than simple discrete electron transfers. It is, nevertheless, possible to draw the curv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tosylate
In organic chemistry, a toluenesulfonyl group (tosyl group, abbreviated Ts or Tos) is a univalent functional group with the chemical formula –. It consists of a tolyl group, –, joined to a sulfonyl group, ––, with the open valence on sulfur. This group is usually derived from the compound tosyl chloride, (abbreviated TsCl), which forms esters and amides of toluenesulfonic acid, (abbreviated TsOH). The para orientation illustrated (''p''-toluenesulfonyl) is most common, and by convention ''tosyl'' without a prefix refers to the ''p''-toluenesulfonyl group. The toluenesulfonate (or tosylate) group refers to the – (TsO–) group, with an additional oxygen attached to sulfur and open valence on an oxygen. In a chemical name, the term ''tosylate'' may either refer to the salts containing the anion of ''p''-toluenesulfonic acid, (M = alkali metal, , , etc), or it may refer to esters of ''p''-toluenesulfonic acid, TsOR (R = organyl group). Applications For SN2 reacti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tosyl Chloride
4-Toluenesulfonyl chloride (''p''-toluenesulfonyl chloride, toluene-''p''-sulfonyl chloride) is an organic compound with the formula CH3C6H4SO2Cl. This white, malodorous solid is a reagent widely used in organic synthesis. Abbreviated TsCl or TosCl, it is a derivative of toluene and contains a sulfonyl chloride (−SO2Cl) functional group. Uses In characteristic manner, TsCl converts alcohols (abbreviated ROH) into the corresponding toluenesulfonate esters, or tosyl derivatives ("tosylates"): : CH3C6H4SO2Cl + ROH → CH3C6H4SO2OR + HCl Tosylates can be cleaved with lithium aluminium hydride: : 4 CH3C6H4SO2OR + LiAlH4 → LiAl(O3SC6H4CH3)4 + 4 RH Thus, tosylation followed by reduction allows for removal of a hydroxyl group. Likewise, TsCl is used to prepare sulfonamides from amines: :CH3C6H4SO2Cl + R2NH → CH3C6H4SO2NR2 + HCl The resulting sulfonamides are non-basic and, when derived from primary amines, are even acidic. TsCl reacts with hydrazine to give p- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Base (chemistry)
In chemistry, there are three definitions in common use of the word base, known as Arrhenius bases, Brønsted bases, and Lewis bases. All definitions agree that bases are substances that react with acids, as originally proposed by G.-F. Rouelle in the mid-18th century. In 1884, Svante Arrhenius proposed that a base is a substance which dissociates in aqueous solution to form Hydroxide ions OH−. These ions can react with hydrogen ions (H+ according to Arrhenius) from the dissociation of acids to form water in an acid–base reaction An acid–base reaction is a chemical reaction that occurs between an acid and a base. It can be used to determine pH via titration. Several theoretical frameworks provide alternative conceptions of the reaction mechanisms and their applica .... A base was therefore a metal hydroxide such as Sodium hydroxide, NaOH or Calcium hydroxide, Ca(OH)2. Such aqueous hydroxide solutions were also described by certain characteristic properties. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbanion
In organic chemistry, a carbanion is an anion in which carbon is trivalent (forms three bonds) and bears a formal negative charge (in at least one significant resonance form). Formally, a carbanion is the conjugate base of a carbon acid: :R3CH\, + \ddot^- -> \mathbf + HB where B stands for the base. The carbanions formed from deprotonation of alkanes (at an sp3 carbon), alkenes (at an sp2 carbon), arenes (at an sp2 carbon), and alkynes (at an sp carbon) are known as alkyl, alkenyl (vinyl), aryl, and alkynyl (acetylide) anions, respectively. Carbanions have a concentration of electron density at the negatively charged carbon, which, in most cases, reacts efficiently with a variety of electrophiles of varying strengths, including carbonyl groups, imines/ iminium salts, halogenating reagents (e.g., ''N''-bromosuccinimide and diiodine), and proton donors. A carbanion is one of several reactive intermediates in organic chemistry. In organic synthesis, organolithium reagents a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleophilic Displacement
In chemistry, a nucleophilic substitution is a class of chemical reactions in which an electron-rich chemical species (known as a nucleophile) replaces a functional group within another electron-deficient molecule (known as the electrophile). The molecule that contains the electrophile and the leaving functional group is called the substrate. The most general form of the reaction may be given as the following: :\text\mathbf + \ce + \text\mathbf The electron pair (:) from the nucleophile (Nuc) attacks the substrate () and bonds with it. Simultaneously, the leaving group (LG) departs with an electron pair. The principal product in this case is . The nucleophile may be electrically neutral or negatively charged, whereas the substrate is typically neutral or positively charged. An example of nucleophilic substitution is the hydrolysis of an alkyl bromide, R-Br under basic conditions, where the attacking nucleophile is hydroxyl () and the leaving group is bromide (). :R-Br + OH- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Azirine
Azirines are three-membered heterocyclic unsaturated (i.e. they contain a double bond) compounds containing a nitrogen atom and related to the saturated analogue aziridine. They are highly reactive yet have been reported in a few natural products such as Dysidazirine. There are two isomers of azirine: 1''H''-Azirines with a carbon-carbon double bond are not stable and rearrange to the tautomeric 2''H''-azirine, a compound with a carbon-nitrogen double bond. 2''H''-Azirines can be considered strained imines and are isolable. Preparation 2''H''-Azirine is most often obtained by the thermolysis of vinyl azides. During this reaction, a nitrene is formed as an intermediate. Alternatively, they can be obtained by oxidation of the corresponding aziridine. Azirine can be generated during photolysis of isoxazole. Due to the weak N-O bond, the isoxazole ring tends to collapse under UV irradiation, rearranging to azirine. : Reactions Photolysis of azirines (under 300 nm) is a very e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beckmann Rearrangement
The Beckmann rearrangement, named after the German chemist Ernst Otto Beckmann (1853–1923), is a rearrangement of an oxime functional group to substituted amides. The rearrangement has also been successfully performed on haloimines and nitrones. Cyclic oximes and haloimines yield lactams. The Beckmann rearrangement is often catalyzed by acid; however, other reagents have been known to promote the rearrangement. These include tosyl chloride, thionyl chloride, phosphorus pentachloride, phosphorus pentoxide, triethylamine, sodium hydroxide, trimethylsilyl iodide among others. The Beckmann fragmentation is another reaction that often competes with the rearrangement, though careful selection of promoting reagent and solvent conditions can favor the formation of one over the other, sometimes giving almost exclusively one product. The rearrangement occurs stereospecifically for ketoximes and N-chloro/N-fluoro imines, with the migrating group being anti-periplanar to the leaving gro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
