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Dicarbonates
In organic chemistry, a dicarbonate, also known as a pyrocarbonate, is a compound containing the divalent ��O−(C=O)−O−(C=O)−O−or −− functional group, which consists of two carbonate groups sharing an oxygen atom. These compounds can be viewed as double esters of a hypothetical dicarbonic acid, or HO−(C=O)−O−(C=O)−OH. Two important examples are dimethyl dicarbonate H3C−C2O5−CH3 and di-''tert''-butyl dicarbonate (H3C−)3C−C2O5−C(−CH3)3. It is one of the oxocarbon anions, consisting solely of oxygen and carbon. Dicarbonate salts are apparently unstable at ambient conditions, but can be made under pressure and may have a fleeting existence in carbonate solutions. The term "dicarbonate" is sometimes used erroneously to refer to bicarbonate, the common name of the hydrogencarbonate anion or organic group the ROCO2H. Inorganic salts PbC2O5 can be formed at 30 GPa and 2000K from PbCO3 and CO2. It forms white monoclinic crystals ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimethyl Dicarbonate
Dimethyl dicarbonate (DMDC) is a colorless liquid and a pungent odor at high concentration at room temperature. It is primarily used as a beverage preservative, processing aid, or sterilant ( INS No. 242) being highly active against typical beverage spoiling microorganisms like yeast, bacteria, or mould. Usage Dimethyl dicarbonate is used to stabilize beverages by preventing microbial spoilage. It can be used in various non-alcoholic as well as alcoholic drinks like wine, cider, beer-mix beverages or hard seltzers. Beverage spoiling microbes are killed by methoxycarbonylation of proteins. It acts by inhibiting enzymes involved in the microbial metabolism, e.g. acetate kinase and L-glutamic acid decarboxylase. It has also been proposed that DMDC inhibits the enzymes alcohol dehydrogenase and glyceraldehyde 3-phosphate dehydrogenase by causing the methoxycarbonylation of their histidine components. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Di-tert-butyl Dicarbonate
Di-''tert''-butyl dicarbonate is a reagent widely used in organic synthesis. Since this compound can be regarded formally as the acid anhydride derived from a ''tert''-butoxycarbonyl (Boc) group, it is commonly referred to as Boc anhydride. This pyrocarbonate reacts with amines to give ''N''-''tert''-butoxycarbonyl or so-called Boc derivatives. These carbamate derivatives do not behave as amines, which allows certain subsequent transformations to occur that would be incompatible with the amine functional group. The Boc group can later be removed from the amine using moderately strong acids (e.g., trifluoroacetic acid). Thus, Boc serves as a protective group, for instance in solid phase peptide synthesis. Boc-protected amines are unreactive to most bases and nucleophiles, allowing for the use of the fluorenylmethyloxycarbonyl group (Fmoc) as an orthogonal protecting group. Preparation Di-''tert''-butyl dicarbonate is inexpensive, so it is usually purchased. Classically, this com ... [...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, i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbonate Esters
In organic chemistry, a carbonate ester (organic carbonate or organocarbonate) is an ester of carbonic acid. This functional group consists of a carbonyl group flanked by two alkoxy groups. The general structure of these carbonates is and they are related to esters (), ethers () and also to the inorganic carbonates. Monomers of polycarbonate (e.g. Makrolon or Lexan) are linked by carbonate groups. These polycarbonates are used in eyeglass lenses, compact discs, and bulletproof glass. Small carbonate esters like dimethyl carbonate, ethylene carbonate, propylene carbonate are used as solvents, dimethyl carbonate is also a mild methylating agent. Structures Carbonate esters have planar OC(OC)2 cores, which confers rigidity. The unique O=C bond is short (1.173 Ã… in the depicted example), while the C-O bonds are more ether-like (the bond distances of 1.326 Ã… for the example depicted). Carbonate esters can be divided into three structural classes: acyclic, cyclic, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxyanions
An oxyanion, or oxoanion, is an ion with the generic formula (where A represents a chemical element and O represents an oxygen atom). Oxyanions are formed by a large majority of the chemical elements. The formulae of simple oxyanions are determined by the octet rule. The corresponding oxyacid of an oxyanion is the compound . The structures of condensed oxyanions can be rationalized in terms of AO''n'' polyhedral units with sharing of corners or edges between polyhedra. The oxyanions (specifically, phosphate and polyphosphate esters) adenosine monophosphate (AMP), adenosine diphosphate (ADP) and adenosine triphosphate (ATP) are important in biology. Monomeric oxyanions The formula of monomeric oxyanions, , is dictated by the oxidation state of the element A and its position in the periodic table. Elements of the first row are limited to a maximum coordination number of 4. However, none of the first row elements has a monomeric oxyanion with that coordination number. Instead, carb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tricarbonate
In organic chemistry, a tricarbonate is a compound containing the divalent ��O–(C=O)–O–(C=O)–O–(C=O)–O–functional group, which consists of three carbonate groups in tandem, sharing two oxygen atoms. These compounds can be viewed as double esters of a hypothetical tricarbonic acid, HO–(C=O)–O–(C=O)–O–(C=O)–OH. An important example is di-''tert''-butyl tricarbonate (H3C–)3C–C3O7–C(–CH3)3, a chemical reagent (colorless prisms that melt at 62–63 °C with decomposition, soluble in pentane Pentane is an organic compound with the formula C5H12—that is, an alkane with five carbon atoms. The term may refer to any of three structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, pentane means exclusively the ' ...).Barry M. Pope, Yutaka Yamamoto, and D. Stanley Tarbell (1977)"Di-''tert''-Butyl Dicarbonate" ''Organic Syntheses'', Vol. 57, p.45; Coll. Vol. 6 (1988) p.418 The term "tricarbonate" is sometimes used for salts ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrosulfate
In chemistry, disulfate or pyrosulfate is the anion with the molecular formula . Disulfate is the IUPAC name. It has a dichromate-like structure and can be visualised as two corner-sharing SO4 tetrahedra, with a bridging oxygen atom. In this anion, sulfur has an oxidation state of +6. Disulfate is the conjugate base of the hydrogen disulfate (hydrogen pyrosulfate) ion , which in turn is the conjugate base of disulfuric acid (pyrosulfuric acid). See also * Potassium pyrosulfate * Sodium pyrosulfate * Pyrophosphate In chemistry, pyrophosphates are phosphorus oxyanions that contain two phosphorus atoms in a P–O–P linkage. A number of pyrophosphate salts exist, such as disodium pyrophosphate (Na2H2P2O7) and tetrasodium pyrophosphate (Na4P2O7), among o ... * Pyrocarbonate References {{reflist Sulfur oxyanions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrophosphate
In chemistry, pyrophosphates are phosphorus oxyanions that contain two phosphorus atoms in a P–O–P linkage. A number of pyrophosphate salts exist, such as disodium pyrophosphate (Na2H2P2O7) and tetrasodium pyrophosphate (Na4P2O7), among others. Often pyrophosphates are called diphosphates. The parent pyrophosphates are derived from partial or complete neutralization of pyrophosphoric acid. The pyrophosphate bond is also sometimes referred to as a phosphoanhydride bond, a naming convention which emphasizes the loss of water that occurs when two phosphates form a new P–O–P bond, and which mirrors the nomenclature for anhydrides of carboxylic acids. Pyrophosphates are found in ATP and other nucleotide triphosphates, which are important in biochemistry. The term pyrophosphate is also the name of esters formed by the condensation of a phosphorylated biological compound with inorganic phosphate, as for dimethylallyl pyrophosphate. This bond is also referred to as a high- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peroxodicarbonate
In chemistry, peroxydicarbonate (sometimes peroxodicarbonate) is a divalent anion with the chemical formula . It is one of the oxocarbon anions, which consist solely of carbon and oxygen. Its molecular structure can be viewed as two carbonate anions joined so as to form a peroxide bridge –O–O–. The anion is formed, together with peroxocarbonate , at the negative electrode during electrolysis of molten lithium carbonate. The anion can also be obtained by electrolysis of a saturated solution of rubidium carbonate in water. In addition, the peroxodicarbonate anion can be obtained by electrosynthesis on boron doped diamond (BDD) during water oxidation. The formal oxidation of two carbonate ions takes place at the anode. Due to the high oxidation potential of the peroxodicarbonate anion, a high anodic overpotential is necessary. This is even more important if hydroxyl radicals are involved in the formation process. Recent publications show that a concentration of 282 mmol/L of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxalate
Oxalate (IUPAC: ethanedioate) is an anion with the formula C2O42−. This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (Na2C2O4), and several esters such as dimethyl oxalate (C2O4(CH3)2). It is a conjugate base of oxalic acid. At neutral pH in aqueous solution, oxalic acid converts completely to oxalate. Relationship to oxalic acid The dissociation of protons from oxalic acid proceeds in a stepwise manner; as for other polyprotic acids, loss of a single proton results in the monovalent hydrogenoxalate anion . A salt with this anion is sometimes called an acid oxalate, monobasic oxalate, or hydrogen oxalate. The equilibrium constant ( ''K''a) for loss of the first proton is (p''K''a = 1.27). The loss of the second proton, which yields the oxalate ion, has an equilibrium constant of (p''K''a = 4.28). These values imply, in solutions with neutral pH, no oxalic acid and only tra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Group
In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it unchanged. In three dimensions, space groups are classified into 219 distinct types, or 230 types if chiral copies are considered distinct. Space groups are discrete cocompact groups of isometries of an oriented Euclidean space in any number of dimensions. In dimensions other than 3, they are sometimes called Bieberbach groups. In crystallography, space groups are also called the crystallographic or Fedorov groups, and represent a description of the symmetry of the crystal. A definitive source regarding 3-dimensional space groups is the ''International Tables for Crystallography'' . History Space groups in 2 dimensions are the 17 wallpaper groups which have been known for several centuries, though the proof that the list was compl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
