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MACHO Catalyst
In homogeneous catalysis, MACHO catalysts are metal complexes containing MACHO ligands, which are of the type HN(CH2CH2PR2)2, where R is typically phenyl or isopropyl. Complexes with ruthenium(II) and iridium(III) have received much attention for their ability to hydrogenate polar bonds such as those in esters and even carbon dioxide. The catalysts appear to operate via intermediates where the amine proton and the hydride ligand both interact with the substrate. The Ru-MACHO catalyst have been commercialized for the synthesis of 1,2-propanediol from bio-derived methyl lactate.{{cite journal , doi=10.1038/s41570-018-0049-z, title=The role of the metal-bound NāH functionality in Noyori-type molecular catalysts, year=2018, last1=Dub, first1=Pavel A., last2=Gordon, first2=John C., s2cid=106394152, journal=Nature Reviews Chemistry, volume=2, issue=12, pages=396ā408 See also * 1,5-Diaza-3,7-diphosphacyclooctanes, phosphine amine ligands used in hydrogen evolution * Noyori asymmet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homogeneous Catalysis
In chemistry, homogeneous catalysis is catalysis by a soluble catalyst in a solution. Homogeneous catalysis refers to reactions where the catalyst is in the same phase as the reactants, principally in solution. In contrast, heterogeneous catalysis describes processes where the catalysts and substrate are in distinct phases, typically solid-gas, respectively. The term is used almost exclusively to describe solutions and implies catalysis by organometallic compounds. Homogeneous catalysis is an established technology that continues to evolve. An illustrative major application is the production of acetic acid. Enzymes are examples of homogeneous catalysts. Examples Acid catalysis The proton is a pervasive homogeneous catalyst because water is the most common solvent. Water forms protons by the process of self-ionization of water. In an illustrative case, acids accelerate (catalyze) the hydrolysis of esters: :CH3CO2CH3 + H2O CH3CO2H + CH3OH At neutral pH, aqueous solutions of most e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metal Complex
A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many metal-containing compounds, especially those that include transition metals (elements like titanium that belong to the Periodic Table's d-block), are coordination complexes. Nomenclature and terminology Coordination complexes are so pervasive that their structures and reactions are described in many ways, sometimes confusingly. The atom within a ligand that is bonded to the central metal atom or ion is called the donor atom. In a typical complex, a metal ion is bonded to several donor atoms, which can be the same or different. A polydentate (multiple bonded) ligand is a molecule or ion that bonds to the central atom through several of the ligand's atoms; ligands with 2, 3, 4 or even 6 bonds to the central atom are common. These compl ... [...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, ice caps, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metal Hydride
In chemistry, a hydride is formally the anion of hydrogen( H−). The term is applied loosely. At one extreme, all compounds containing covalently bound H atoms are called hydrides: water (H2O) is a hydride of oxygen, ammonia is a hydride of nitrogen, etc. For inorganic chemists, hydrides refer to compounds and ions in which hydrogen is covalently attached to a less electronegative element. In such cases, the H centre has nucleophilic character, which contrasts with the protic character of acids. The hydride anion is very rarely observed. Almost all of the elements form binary compounds with hydrogen, the exceptions being He, Ne, Ar, Kr, Pm, Os, Ir, Rn, Fr, and Ra. Exotic molecules such as positronium hydride have also been made. Bonds Bonds between hydrogen and the other elements range from highly to somewhat covalent. Some hydrides, e.g. boron hydrides, do not conform to classical electron-counting rules and the bonding is described in terms of multi-centered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1,2-Propanediol
Propylene glycol (IUPAC name: propane-1,2-diol) is a viscous, colorless liquid, which is nearly odorless but possesses a faintly sweet taste. Its chemical formula is CH3CH(OH)CH2OH. Containing two alcohol groups, it is classed as a diol. It is miscible with a broad range of solvents, including water, acetone, and chloroform. In general, glycols are non-irritating and have very low volatility. It is produced on a large scale primarily for the production of polymers. In the European Union, it has E-number E1520 for food applications. For cosmetics and pharmacology, the number is E490. Propylene glycol is also present in propylene glycol alginate, which is known as E405. Propylene glycol is a compound which is GRAS (generally recognized as safe) by the US Food and Drug Administration under 21 CFR x184.1666, and is also approved by the FDA for certain uses as an indirect food additive. Propylene glycol is approved and used as a vehicle for topical, oral, and some intravenous pharm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methyl Lactate
Methyl lactate, also known as lactic acid methyl ester, is the organic compound with the formula CH3CH(OH)CO2CH3. It is the methyl ester of lactic acid. A colorless liquid, it is the simplest chiral ester. Being naturally derived, it is readily available as a single enantiomer. Uses It is a solvent for nitrocellulose, cellulose acetate, cellulose acetobutyrate and cellulose acetopropionate. It is used in the manufacture of lacquers and dopes where it contributes high tolerance for diluents, good flaw and blush resistance."Industrial Solvents Handbook" by Ernest W. Flick. 5th Edition. William Andrew Inc., 1998. , The synthesis of 1,2-propanediol from methyl lactate has been commercialized using a MACHO catalyst. See also *Ethyl lactate Ethyl lactate, also known as lactic acid ethyl ester, is the organic compound with the formula CH3CH(OH)CO2CH2CH3. It is the ethyl ester of lactic acid. A colorless liquid, it is a chiral ester. Being naturally derived, it is readily availab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1,5-Diaza-3,7-diphosphacyclooctanes
1,5-Diaza-3,7-diphosphacyclooctanes are organophosphorus compounds with the formula 'NCHP(R)CH often abbreviated PN. They are air-sensitive white solids that are soluble in organic solvents. The ligands exist as meso and d,l-diastereomers, but only the meso forms function as bidentate ligands. Some metal-PN complexes catalyze the hydrogen evolution reaction as well as the oxidation of hydrogen (H). The catalytic mechanism involves the interaction of substrate with the amines in the second coordination sphere. Synthesis and reactions The ligands are prepared by the condensation of a primary phosphine, formaldehyde, and a primary amine: :2 RPH + 4 CHO + 2 RNH ā NCHP(R')CH + 4 HO Diazadiphosphacyclooctanes function as chelating diphos phine ligands. Typical nickel complexes contain two such ligands are give the formula i(PN) Cationic complexes of these PN and related ligands often exhibit enhanced reactivity toward H. These complexes serve as electrocatalysts for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noyori Asymmetric Hydrogenation
In chemistry, the Noyori asymmetric hydrogenation refers to methodology for enantioselective reduction of ketones and related functional groups. This methodology was introduced by Ryoji Noyori, who shared the Nobel Prize in Chemistry in 2001 for contributions to asymmetric hydrogenation. These hydrogenations are used in the production of several drugs, such as the antibacterial levofloxin, the antibiotic carbapenem, and the antipsychotic agent BMS181100. History The stoichiometric asymmetric reduction of ketones has long been known, e.g., using boron hydrides. The catalytic asymmetric hydrogenation of ketones was demonstrated with catalysts based on BINAP-Ru halides and carboxylates. Even though the BINAP-Ru dihalide catalyst could reduce functionalized ketones, the hydrogenation of simple ketones remained an unsolved. This challenge was solved with precatalysts of the type RuCl2(diphosphane)(diamine). These catalysts preferentially reduce ketones and aldehydes, leaving olefins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shvo Catalyst
The Shvo catalyst is an organoruthenium compound that catalyzes the hydrogenation of polar functional groups including aldehydes, ketones and imines. The compound is of academic interest as an early example of a catalyst for transfer hydrogenation that operates by an "outer sphere mechanism". Related derivatives are known where p-tolyl replaces some of the phenyl groups. Shvo's catalyst represents a subset of homogeneous hydrogenation catalysts that involves both metal and ligand in its mechanism. Synthesis and structure The catalyst is named after Youval Shvo, who uncovered it through studies on the effect of diphenylacetylene on the catalytic properties of triruthenium dodecacarbonyl. The reaction of diphenylacetylene and Ru3(CO)12 gives the piano stool complex . Subsequent hydrogenation of this tricarbonyl affords Shvo's catalyst. Y. Blum, D. Reshef, and Y. Shvo. H-transfer catalysis with Ru3(CO)12. Tetrahedron Lett. 22(16) 1981, pp. 1541-1544. Blum, Y.; Shvo, Y. Isr. J. Chem. 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homogeneous Catalysis
In chemistry, homogeneous catalysis is catalysis by a soluble catalyst in a solution. Homogeneous catalysis refers to reactions where the catalyst is in the same phase as the reactants, principally in solution. In contrast, heterogeneous catalysis describes processes where the catalysts and substrate are in distinct phases, typically solid-gas, respectively. The term is used almost exclusively to describe solutions and implies catalysis by organometallic compounds. Homogeneous catalysis is an established technology that continues to evolve. An illustrative major application is the production of acetic acid. Enzymes are examples of homogeneous catalysts. Examples Acid catalysis The proton is a pervasive homogeneous catalyst because water is the most common solvent. Water forms protons by the process of self-ionization of water. In an illustrative case, acids accelerate (catalyze) the hydrolysis of esters: :CH3CO2CH3 + H2O CH3CO2H + CH3OH At neutral pH, aqueous solutions of most e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
