|
Concerted Metalation Deprotonation
Concerted metalation-deprotonation (CMD) is a mechanistic pathway through which transition-metal catalyzed C–H activation reactions can take place. In a CMD pathway, the C–H bond of the substrate is cleaved and the new C–Metal bond forms through a single transition state. This process does not go through a metal species that is bound to the cleaved hydrogen atom. Instead, a carboxylate or carbonate base deprotonates the substrate. The first proposal of a concerted metalation deprotonation pathway was by S. Winstein and T. G. Traylor in 1955 for the acetolysis of diphenylmercury. It was found to be the lowest energy transition state in a number of computational studies, was experimentally confirmed through NMR experiments, and has been hypothesized to occur in mechanistic studies. While there are a number of different possible mechanisms for C–H activation, a CMD pathway is common for high valent, late transition metals like PdII, RhIII, IrIII, and RuII. The C–H bonds that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon–hydrogen Bond Activation
In organic chemistry, carbon–hydrogen bond functionalization ( functionalization) is a type of organic reaction in which a carbon–hydrogen bond is cleaved and replaced with a bond (where X is usually carbon, oxygen, or nitrogen). The term usually implies that a transition metal is involved in the cleavage process. Reactions classified by the term typically involve the hydrocarbon first to react with a metal catalyst to create an organometallic complex in which the hydrocarbon is coordinated to the inner-sphere of a metal, either via an intermediate "alkane or arene complex" or as a transition state leading to a "" intermediate. The intermediate of this first step (known as activation and sometimes used interchangeably with functionalization) can then undergo subsequent reactions to produce the functionalized product. Important to this definition is the requirement that during the cleavage event, the hydrocarbyl species remains associated in the inner-sphere and under ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzene
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon. Benzene is a natural constituent of petroleum and is one of the elementary petrochemicals. Due to the cyclic continuous pi bonds between the carbon atoms, benzene is classed as an aromatic hydrocarbon. Benzene is a colorless and highly flammable liquid with a sweet smell, and is partially responsible for the aroma of gasoline. It is used primarily as a precursor to the manufacture of chemicals with more complex structure, such as ethylbenzene and cumene, of which billions of kilograms are produced annually. Although benzene is a major industrial chemical, it finds limited use in consumer items because of its toxicity. History Discovery The word "''benzene''" derives from "''gum benzoin''" (benzoin res ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzoic Acid
Benzoic acid is a white (or colorless) solid organic compound with the formula , whose structure consists of a benzene ring () with a carboxyl () substituent. It is the simplest aromatic carboxylic acid. The name is derived from gum benzoin, which was for a long time its only source. Benzoic acid occurs naturally in many plants and serves as an intermediate in the biosynthesis of many secondary metabolites. Salts of benzoic acid are used as food preservatives. Benzoic acid is an important precursor for the industrial synthesis of many other organic substances. The salts and esters of benzoic acid are known as benzoates . History Benzoic acid was discovered in the sixteenth century. The dry distillation of gum benzoin was first described by Nostradamus (1556), and then by Alexius Pedemontanus (1560) and Blaise de Vigenère (1596). Justus von Liebig and Friedrich Wöhler determined the composition of benzoic acid. These latter also investigated how hippuric acid is related ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acetic Acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component of vinegar apart from water and other trace elements. Acetic acid is the second simplest carboxylic acid (after formic acid). It is an important Reagent, chemical reagent and industrial chemical, used primarily in the production of cellulose acetate for photographic film, polyvinyl acetate for wood Adhesive, glue, and synthetic fibres and fabrics. In households, diluted acetic acid is often used in descaling agents. In the food industry, acetic acid is controlled by the E number, food additive code E260 as an acidity regulator and as a condiment. In biochemistry, the acetyl group, derived from acetic acid, is fundamental to all forms of life. When bound to coenzyme A, it is central to the metabolism of carbohydrates and fats. The global ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pivalic Acid
Pivalic acid is a carboxylic acid with a molecular formula of (CH3)3CCO2H. This colourless, odiferous organic compound is solid at room temperature. A common abbreviation for the pivalyl or pivaloyl group (''t''-BuC(O)) is Piv and for pivalic acid (''t''-BuC(O)OH) is PivOH. Preparation Industrial route Pivalic acid is prepared by hydrocarboxylation of isobutene via the Koch reaction: :(CH3)2C=CH2 + CO + H2O → (CH3)3CCO2H Such reactions require an acid catalyst such as hydrogen fluoride. ''tert''-Butyl alcohol and isobutyl alcohol can also be used in place of isobutene. Globally, several million kilograms are produced annually. Pivalic acid is also economically recovered as a byproduct from the production of semisynthetic penicillins like ampicillin and amoxycillin. Laboratory methods It was originally prepared by the oxidation of pinacolone with chromic acid and by the hydrolysis of ''tert''-butyl cyanide. Convenient laboratory routes proceed via ''tert''-butyl chloride via ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Principle Of Microscopic Reversibility
The principle of microscopic reversibility in physics and chemistry is twofold: * First, it states that the microscopic detailed dynamics of particles and fields is time-reversible because the microscopic equations of motion are symmetric with respect to inversion in time (T-symmetry); * Second, it relates to the statistical description of the kinetics of macroscopic or mesoscopic systems as an ensemble of elementary processes: collisions, elementary transitions or reactions. For these processes, the consequence of the microscopic T-symmetry is: ''Corresponding to every individual process there is a reverse process, and in a state of equilibrium the average rate of every process is equal to the average rate of its reverse process.'' History of microscopic reversibility The idea of microscopic reversibility was born together with physical kinetics. In 1872, Ludwig Boltzmann represented kinetics of gases as statistical ensemble of elementary collisions.Boltzmann, L. (1964), Lectures on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infrared Spectroscopy
Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) is the measurement of the interaction of infrared radiation with matter by absorption, emission, or reflection. It is used to study and identify chemical substances or functional groups in solid, liquid, or gaseous forms. It can be used to characterize new materials or identify and verify known and unknown samples. The method or technique of infrared spectroscopy is conducted with an instrument called an infrared spectrometer (or spectrophotometer) which produces an infrared spectrum. An IR spectrum can be visualized in a graph of infrared light absorbance (or transmittance) on the vertical axis vs. frequency, wavenumber or wavelength on the horizontal axis. Typical units of wavenumber used in IR spectra are reciprocal centimeters, with the symbol cm−1. Units of IR wavelength are commonly given in micrometers (formerly called "microns"), symbol μm, which are related to the wavenumber in a reciprocal way. A com ... [...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] |
Acetic Acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component of vinegar apart from water and other trace elements. Acetic acid is the second simplest carboxylic acid (after formic acid). It is an important Reagent, chemical reagent and industrial chemical, used primarily in the production of cellulose acetate for photographic film, polyvinyl acetate for wood Adhesive, glue, and synthetic fibres and fabrics. In households, diluted acetic acid is often used in descaling agents. In the food industry, acetic acid is controlled by the E number, food additive code E260 as an acidity regulator and as a condiment. In biochemistry, the acetyl group, derived from acetic acid, is fundamental to all forms of life. When bound to coenzyme A, it is central to the metabolism of carbohydrates and fats. The global ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perchloric Acid
Perchloric acid is a mineral acid with the formula H Cl O4. Usually found as an aqueous solution, this colorless compound is a stronger acid than sulfuric acid, nitric acid and hydrochloric acid. It is a powerful oxidizer when hot, but aqueous solutions up to approximately 70% by weight at room temperature are generally safe, only showing strong acid features and no oxidizing properties. Perchloric acid is useful for preparing perchlorate salts, especially ammonium perchlorate, an important rocket fuel component. Perchloric acid is dangerously corrosive and readily forms potentially explosive mixtures. History Perchloric acid was first synthesized (together with potassium perchlorate) by Austrian chemist and called "oxygenated chloric acid" in mid-1810s; French pharmacist Georges-Simon Serullas introduced the modern designation along with discovering its solid monohydrate (which he, however, mistook for an anhydride). Production Perchloric acid is produced industrially by two r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2.png "Click for more on -> Benzene")
