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Semitrione
Semidiones are radical anions analogous to semiquinones, obtained from the one-electron reduction of non-quinone Conjugated system, conjugated dicarbonyls. The simplest possible semidiones are derived from 1,2-dicarbonyls and have structure , making them the second member of a homologous series starting with ketyl radicals and continuing with ''semitriones''. They are often transient intermediates, appearing in reactions such as the final reduction step of the acyloin condensation. Benzil semidione (), synthesized by Auguste Laurent in 1836, is believed to have been the first radical ion ever characterized. Semidehydroascorbate is a relatively stable semitrione produced by hydrogen abstraction from ascorbate (Vitamin C Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits, berries and vegetables. It is also a generic prescription medication and in some countries is sold as a non-prescription di ...). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemistry Of Ascorbic Acid
Ascorbic acid is an organic compound with formula , originally called hexuronic acid. It is a white solid, but impure samples can appear yellowish. It dissolves freely in water to give mildly acidic solutions. It is a mild reducing agent. Ascorbic acid exists as two enantiomers (mirror-image isomers), commonly denoted "" (for "levo") and "" (for "dextro"). The isomer is the one most often encountered: it occurs naturally in many foods, and is one form ("vitamer") of vitamin C, an essential nutrient for humans and many animals. Deficiency of vitamin C causes scurvy, formerly a major disease of sailors in long sea voyages. It is used as a food additive and a dietary supplement for its antioxidant properties. The "" form ( erythorbic acid) can be made by chemical synthesis, but has no significant biological role. Etymology The term ''ascorbic'' means antiscruvy and denotes the ability to fight off scurvy. It is related to combating Vitamin C deficiency. History The antiscorb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acyloin Condensation
Acyloin condensation is a Redox, reductive coupling of two carboxylic esters using Impurity, impure metallic sodium to yield an α-hydroxyketone, also known as an acyloin. The reaction is most successful when ''R'' is Aliphatic compound, aliphatic and Saturated compound, saturated, and typically performed with a silyl chloride reactant to Trapping (chemistry), trap the product as a Silyl enol ether, disilyl enediol ether. The reaction is performed in aprotic solvents with a high boiling point, such as benzene and toluene, in an Inert atmosphere technique, oxygen-free atmosphere (as even traces of oxygen interfere with the reaction path and reduce the yield). Protic solvents effect the Bouveault-Blanc reduction, Bouveault-Blanc ester reduction rather than condensation. Independent of Concentration, dilution, acyloin condensation of a Diesters, diester favours intramolecular cyclisation (for all but the smallest rings) over intermolecular polymerisation. This effect is belie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free Radicals
In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired electron, unpaired valence electron. With some exceptions, these unpaired electrons make radicals highly chemical reaction, chemically reactive. Many radicals spontaneously dimer (chemistry), dimerize. Most organic radicals have short lifetimes. A notable example of a radical is the hydroxyl radical (HO·), a molecule that has one unpaired electron on the oxygen atom. Two other examples are triplet oxygen and methylene radical, triplet carbene (꞉) which have two unpaired electrons. Radicals may be generated in a number of ways, but typical methods involve redox reactions. Ionizing radiation, heat, electrical discharges, and electrolysis are known to produce radicals. Radicals are intermediates in many chemical reactions, more so than is apparent from the balanced equations. Radicals are important in combustion, atmospheric chemistry, polymerization, Plasma (phy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vitamin C
Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits, berries and vegetables. It is also a generic prescription medication and in some countries is sold as a non-prescription dietary supplement. As a therapy, it is used to prevent and treat scurvy, a disease caused by vitamin C deficiency. Vitamin C is an essential nutrient involved in the repair of tissue, the formation of collagen, and the enzymatic production of certain neurotransmitters. It is required for the functioning of several enzymes and is important for immune system function. It also functions as an antioxidant. Vitamin C may be taken by mouth or by intramuscular, subcutaneous or intravenous injection. Various health claims exist on the basis that moderate vitamin C deficiency increases disease risk, such as for the common cold, cancer or COVID-19. There are also claims of benefits from vitamin C supplementation in excess of the recommended d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Annalen Der Pharmacie
''Justus Liebig's Annalen der Chemie'' (often cited as ''Liebigs Annalen'') was one of the oldest and historically most important journals in the field of organic chemistry worldwide. It was established in 1832 and edited by Justus von Liebig with Friedrich Wöhler and others until Liebig's death in 1873. The journal was originally titled ''Annalen der Pharmacie''; its name was changed to ''Justus Liebig's Annalen der Chemie'' in 1874. In its first decades of publishing, the journal was both a periodical containing news of the chemical and pharmaceutical fields and a publisher of primary research. During this time, it was noted to contain rebuttals and criticism of the works it published, inserted by Justus von Liebig during his tenure as an editor. After 1874, changes were made to editorial policies, and the journal published only completed research; later on, in the 20th century, its focus was narrowed to only print articles on organic chemistry, though it had always placed emph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radical Ion
In organic chemistry, a radical anion is a Radical (chemistry), free radical species that carries a charge (chemistry), negative charge. Radical anions are encountered in organic chemistry as reduced derivatives of polycyclic aromatic compounds, e.g. sodium naphthenide. An example of a non-carbon radical anion is the superoxide anion, formed by transfer of one electron to an oxygen molecule. Radical anions are typically indicated by M^. Polycyclic radical anions Many aromatic compounds can undergo one-electron reduction by alkali metals. The electron is transferred from the alkali metal ion to an unoccupied antibonding p-p п* orbital of the aromatic molecule. This transfer is usually only energetically favorable if the aprotic solvent efficiently solvates the alkali metal ion. Effective solvents are those that bind to the alkali metal cation: diethyl ether < tetrahydrofurane, THF < dimethoxyethane, 1,2-dimethoxyethane < HMPA. In principle any unsaturated molecule can form a r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Auguste Laurent
Auguste Laurent (14 November 1807 – 15 April 1853) was a French chemist who helped in the founding of organic chemistry with his discoveries of trichloroethylene, anthracene, phthalic acid, and carbolic acid. He devised a systematic nomenclature for organic chemistry based on structural grouping of atoms within molecules to determine how the molecules combine in organic reactions. He studied under Jean-Baptiste Dumas as a laboratory assistant. At that time, the weight of carbon was considered to be 6. Laurent thought that a weight of 12 was more logical, and started drawing structures on that basis. He published his work in conjunction with Charles Frédéric Gerhardt. Shunned by Dumas, he eked out a living teaching in the mineral engineering lab - where he taught a young Louis Pasteur how to crystalize tartaric acid. Laurent died in Paris from tuberculosis. Alexander Williamson in England read Laurent's writing, leading to the Williamson Ether Synthesis that confirmed t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzil
Benzil (i.e. Bz2, systematically known as 1,2-diphenylethane-1,2-dione) is the organic compound with the formula ( C6H5 CO)2, generally abbreviated ( PhCO)2. This yellow solid is one of the most common diketones. Its main use is as a photoinitiator in polymer chemistry.Hardo Siegel, Manfred Eggersdorfer "Ketones" in Ullmann's Encyclopedia of Industrial Chemistry Wiley-VCH, 2002 by Wiley-VCH, Weinheim. Structure The compound's most noteworthy structural feature is the long carbon-carbon bond of 1.54 Å, which indicates the absence of pi-bonding between the two carbonyl centers. The PhCO centers are planar, but the pair of benzoyl groups are twisted with respect to the other with a dihedral angle of 117°. In less hindered analogues (glyoxal, biacetyl, oxalic acid derivatives), the (RCO)2 group adopts a planar, anti-conformation. Applications Most benzil can be used as a photoinitiator in the free-radical curing of polymer networks. It absorbs ultraviolet radiation at a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reactive Intermediates
In chemistry, a reactive intermediate or an intermediate is a short-lived, high-energy, highly reactive molecule. When generated in a chemical reaction, it will quickly convert into a more stable molecule. Only in exceptional cases can these compounds be isolated and stored, e.g. low temperatures, matrix isolation. When their existence is indicated, reactive intermediates can help explain how a chemical reaction takes place. Most chemical reactions take more than one elementary step to complete, and a reactive intermediate is a high-energy, hence unstable, product that exists only in one of the intermediate steps. The series of steps together make a reaction mechanism. A reactive intermediate differs from a reactant or product or a simple reaction intermediate only in that it cannot usually be isolated but is sometimes observable only through fast spectroscopic methods. It is stable in the sense that an elementary reaction forms the reactive intermediate and the elementary reacti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radical Anion
In organic chemistry, a radical anion is a free radical species that carries a negative charge. Radical anions are encountered in organic chemistry as reduced derivatives of polycyclic aromatic compounds, e.g. sodium naphthenide. An example of a non-carbon radical anion is the superoxide anion, formed by transfer of one electron to an oxygen molecule. Radical anions are typically indicated by M^. Polycyclic radical anions Many aromatic compounds can undergo one-electron reduction by alkali metals. The electron is transferred from the alkali metal ion to an unoccupied antibonding p-p п* orbital of the aromatic molecule. This transfer is usually only energetically favorable if the aprotic solvent efficiently solvates the alkali metal ion. Effective solvents are those that bind to the alkali metal cation: diethyl ether < THF < [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ketyl
A ketyl group in organic chemistry is an anion radical that contains a group R2C−O•. It is the product of the 1-electron reduction of a ketone. Another mesomeric structure has the radical position on carbon and the negative charge on oxygen. : Ketyls can be formed as radical anions by one-electron reduction of carbonyls with alkali metals. Sodium and potassium metal reduce benzophenone in THF solution to the soluble ketyl radical. Ketyls are also invoked as intermediates in the pinacol coupling reaction. Reactions Water The ketyl radicals derived from the reaction of sodium and benzophenone is a common laboratory desiccant. Ketyls react quickly with water, peroxides, and with oxygen. Thus, the deep purple coloration qualitatively indicates dry, peroxide-free, and oxygen-free conditions. The method for drying is still popular in many laboratories due to its ability to produce such pure solvent quickly. An alternative option for chemists interested only in water-free so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
