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Bithiophene
2,2′-Bithiophene is the organic compound. It is a colorless solid, although commercial samples are often greenish. It is the most common of the three isomers with formula (C4H3S)2. The other two isomers have the connectivity 2,3′- and 3,3′-. The compound is typically prepared by cross-coupling starting from 2-halothiophenes. X-ray crystallography shows that the two rings are coplanar, unlike the situation for biphenyl. Occurrence A number of bi- as well as terthiophenes exist naturally, invariably with substituents at the positions flanking sulfur. In terms of the biosynthesis, bithiophenes are proposed to be derived from polyacetylenic precursors, which in turn are the products of dehydrogenation of oleic acid Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish. In chemical terms, oleic acid is classified as a monounsaturated omega .... Accordin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thiophene
Thiophene is a heterocyclic compound with the formula C4H4S. Consisting of a planar five-membered ring, it is aromatic as indicated by its extensive substitution reactions. It is a colorless liquid with a benzene-like odor. In most of its reactions, it resembles benzene. Compounds analogous to thiophene include furan (C4H4O), selenophene (C4H4Se) and pyrrole (C4H4NH), which each vary by the heteroatom in the ring. Isolation and occurrence Thiophene was discovered as a contaminant in benzene. It was observed that isatin (an indole) forms a blue dye if it is mixed with sulfuric acid and crude benzene. The formation of the blue indophenin had long been believed to be a reaction of benzene itself. Viktor Meyer was able to isolate thiophene as the actual substance responsible for this reaction. Thiophene and especially its derivatives occur in petroleum, sometimes in concentrations up to 1–3%. The thiophenic content of oil and coal is removed via the hydrodesulfurization (HDS) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biphenyl
Biphenyl (also known as diphenyl, phenylbenzene, 1,1′-biphenyl, lemonene or BP) is an organic compound that forms colorless crystals. Particularly in older literature, compounds containing the functional group consisting of biphenyl less one hydrogen (the site at which it is attached) may use the prefixes xenyl or diphenylyl. It has a distinctively pleasant smell. Biphenyl is an aromatic hydrocarbon with a molecular formula (C6H5)2. It is notable as a starting material for the production of polychlorinated biphenyls (PCBs), which were once widely used as dielectric fluids and heat transfer agents. Biphenyl is also an intermediate for the production of a host of other organic compounds such as emulsifiers, optical brighteners, crop protection products, and plastics. Biphenyl is insoluble in water, but soluble in typical organic solvents. The biphenyl molecule consists of two connected phenyl rings. Properties and occurrence Biphenyl occurs naturally in coal tar, crude oil, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terthiophene
Terthiophene is the organic compound with the formula 4H3Ssub>2C4H2S. It is an oligomer of the heterocycle thiophene, a shorter oligomer is dithienyl, and the parent polymer is polythiophene. In the most common isomer of terthiophene, two thienyl groups are connected via their 2 positions to a central thiophene, also at the carbon atoms flanking the sulfur. Preparation of terthiophene Terthiophene is prepared by the nickel- or palladium-catalysed coupling reaction of 2,5-dibromothiophene with the Grignard reagent derived from 2-bromothiophene. Properties and applications This isomer is a pigment in African marigolds (''Tagetes'' spp.) and exhibits some biological activity because it sensitizes the formation of singlet oxygen. It is responsible for the insecticidal activity of ''Tagetes minuta''. Together with derivatives of 2,2'-bithiophene, various substituted terthiophenes occur naturally. Examples include 5,5''-dichloro-α-terthiophene, 5-chloro-α-terthiophene, 5-acetyl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The study of the properties, reactions, and syntheses of organic compounds comprise the discipline known as organic chemistry. For historical reasons, a few classes of carbon-containing compounds (e.g., carbonate salts and cyanide salts), along with a few other exceptions (e.g., carbon dioxide, hydrogen cyanide), are not classified as organic compounds and are considered inorganic. Other than those just named, little consensus exists among chemists on precisely which carbon-containing compounds are excluded, making any rigorous definition of an organic compound elusive. Although organic compounds make up only a small percentage of Earth's crust, they are of central importance because all known life is based on organic compounds. Living t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Isomers do not necessarily share similar chemical or physical properties. Two main forms of isomerism are structural or constitutional isomerism, in which ''bonds'' between the atoms differ; and stereoisomerism or spatial isomerism, in which the bonds are the same but the ''relative positions'' of the atoms differ. Isomeric relationships form a hierarchy. Two chemicals might be the same constitutional isomer, but upon deeper analysis be stereoisomers of each other. Two molecules that are the same stereoisomer as each other might be in different conformational forms or be different isotopologues. The depth of analysis depends on the field of study or the chemical and physical properties of interest. The English word "isomer" () is a back-for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cross-coupling
In organic chemistry, a cross-coupling reaction is a reaction where two fragments are joined together with the aid of a metal catalyst. In one important reaction type, a main group organometallic compound of the type R-M (R = organic fragment, M = main group center) reacts with an organic halide of the type R'-X with formation of a new carbon–carbon bond in the product R-R'. Cross-coupling reaction are a subset of coupling reactions. It is often used in arylations. Richard F. Heck, Ei-ichi Negishi, and Akira Suzuki were awarded the 2010 Nobel Prize in Chemistry for developing palladium-catalyzed coupling reactions. Mechanism The mechanism generally involves reductive elimination of the organic substituents R and R' on a metal complex of the type LnMR(R') (where L is some arbitrary spectator ligand). The crucial intermediate LnMR(R') is formed in a two step process from a low valence precursor Ln. The oxidative addition of an organic halide (RX) to LnM gives LnMR(X). Subseq ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray Crystallography
X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their crystallographic disorder, and various other information. Since many materials can form crystals—such as salts, metals, minerals, semiconductors, as well as various inorganic, organic, and biological molecules—X-ray crystallography has been fundamental in the development of many scientific fields. In its first decades of use, this method determined the size of atoms, the lengths and types of chemical bonds, and the atomic-scale differences among various mat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biosynthesis
Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. This process often consists of metabolic pathways. Some of these biosynthetic pathways are located within a single cellular organelle, while others involve enzymes that are located within multiple cellular organelles. Examples of these biosynthetic pathways include the production of lipid membrane components and nucleotides. Biosynthesis is usually synonymous with anabolism. The prerequisite elements for biosynthesis include: precursor compounds, chemical energy (e.g. ATP), and catalytic enzymes which may require coenzymes (e.g.NADH, NADPH). These elements create monomers, the building blocks for macromolecules. Some important biological macromolecules include: proteins, which are composed of amino acid monomers joined via peptide bon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dehydrogenation
In chemistry, dehydrogenation is a chemical reaction that involves the removal of hydrogen, usually from an organic molecule. It is the reverse of hydrogenation. Dehydrogenation is important, both as a useful reaction and a serious problem. At its simplest, it is useful way of converting alkanes, which are relatively inert and thus low-valued, to olefins, which are reactive and thus more valuable. Alkenes are precursors to aldehydes (), alcohols (), polymers, and aromatics. As a problematic reaction, the fouling and inactivation of many catalysts arises via coking, which is the dehydrogenative polymerization of organic substrates. Enzymes that catalyze dehydrogenation are called dehydrogenases. Heterogeneous catalytic routes Styrene Dehydrogenation processes are used extensively to produce aromatics in the petrochemical industry. Such processes are highly endothermic and require temperatures of 500 °C and above. Dehydrogenation also converts saturated fats to unsatura ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oleic Acid
Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish. In chemical terms, oleic acid is classified as a monounsaturated omega-9 fatty acid, abbreviated with a lipid number of 18:1 ''cis''-9, and a main product of Δ9 desaturase. It has the formula CH3(CH2)7CH=CH(CH2)7COOH. The name derives from the Latin word ''oleum'', which means oil. It is the most common fatty acid in nature. The salts and esters of oleic acid are called oleates. Occurrence Fatty acids (or their salts) often do not occur as such in biological systems. Instead fatty acids such as oleic acid occur as their esters, commonly triglycerides, which are the greasy materials in many natural oils. Oleic acid is the most common monounsaturated fatty acid in nature. It is found in fats (triglycerides), the phospholipids that make membranes, cholesterol esters, and wax esters. Triglycerides of oleic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1,2-Dithiin
Dithiin is a class of heterocyclic compounds, with the parent members having the formula (C2H2)2S2. Two isomers of this parent are recognized, 1,2- and 1,4-dithiins. Planar dithiins are 8π e− systems, which would lead to antiaromaticity if the structure was planar. Akin to the behavior of cyclooctatetraene, they instead adopt nonplanar structures. Vinyldithiin, a common component of garlic, is a misnomer for 3-vinyl-4''H''-1,2-dithiin. 1,3-dithiins are unknown. 1,4-Dithiins 1,4-Dithiins have been more extensively studied. They are usually prepared by condensation of the equivalent of α-mercaptocarbonyls. For example, the acetal HSCH2CH(OEt)2 converts upon heating to the parent 1,4-dithiin. They are nonplanar and can be oxidized to their radical cations. Photolysis leads to dimerization via a +2cycloaddition. Thianthrene is dibenzo-1,4-dithiin. 1,2-Dithiins 1,2-Dithiins are isomers of but-2-ene-dithials. They tend to be unstable with respect to loss of sulfur and formati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dihydrogen Disulfide
Hydrogen disulfide is the inorganic compound with the formula H2S2. This hydrogen chalcogenide is a pale yellow volatile liquid with a camphor-like odor. It decomposes readily to hydrogen sulfide (H2S) and elemental sulfur.R. Steudel "Inorganic Polysulfanes H2S''n'' with ''n'' > 1" in Elemental Sulfur and Sulfur-Rich Compounds II (Topics in Current Chemistry) 2003, Volume 231, pp 99–125. Structure The structure of hydrogen disulfide is similar to that of hydrogen peroxide, with C2 point group symmetry. Both molecules are distinctly nonplanar. The dihedral angle is 90.6°, compared with 111.5° in H2O2. The H−S−S bond angle is 92°, close to 90° for unhybridized divalent sulfur. Synthesis and reactions Hydrogen disulfide can be synthesised by dissolving alkali metal or alkaline earth metal polysulfides in water. When the solution is mixed with concentrated hydrochloric acid at −15 °C, a yellow oil consisting a mixture of polysulfanes (H2Sn) will pool below the aque ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
