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Rhodium-platinum Oxide
Rhodium-platinum oxide (Rh–Pt oxide), or Nishimura's catalyst, is an inorganic compound used as a hydrogenation catalyst. Uses Rh–Pt oxide is used to reduce various aromatic compounds to their respective cycloalkanes or saturated heterocycles under mild conditions (i.e. often at room temperature and atmospheric pressure). In this application, Rh–Pt oxide is superior to other group 10 catalysts such as platinum dioxide. Furthermore, the catalyst can be used to carryout the reaction with minimal losses of oxygen containing functional groups via hydrogenolysis. Preparation An aqueous solution of rhodium chloride, chloroplatinic acid, and sodium nitrate is evaporated and then fused in a porcelain dish between 460-480°C until the oxides of nitrogen cease (≈10 minutes). The resulting solidified mass is then washed with distilled water and dilute sodium nitrate followed by drying with calcium chloride to yield the catalyst. Typically the ratio of metals used for the cat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inorganic Compound
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemistry''. Inorganic compounds comprise most of the Earth's crust, although the compositions of the deep mantle remain active areas of investigation. Some simple carbon compounds are often considered inorganic. Examples include the allotropes of carbon (graphite, diamond, buckminsterfullerene, etc.), carbon monoxide, carbon dioxide, carbides, and the following salts of inorganic anions: carbonates, cyanides, cyanates, and thiocyanates. Many of these are normal parts of mostly organic systems, including organisms; describing a chemical as inorganic does not necessarily mean that it does not occur within living things. History Friedrich Wöhler's conversion of ammonium cyanate into urea in 1828 is often cited as the starting point of modern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Nitrate
Sodium nitrate is the chemical compound with the formula . This alkali metal nitrate salt is also known as Chile saltpeter (large deposits of which were historically mined in Chile) to distinguish it from ordinary saltpeter, potassium nitrate. The mineral form is also known as nitratine, nitratite or soda niter. Sodium nitrate is a white deliquescent solid very soluble in water. It is a readily available source of the nitrate anion (NO3−), which is useful in several reactions carried out on industrial scales for the production of fertilizers, pyrotechnics, smoke bombs and other explosives, glass and pottery enamels, food preservatives (esp. meats), and solid rocket propellant. It has been mined extensively for these purposes. History The first shipment of saltpeter to Europe arrived in England from Peru in 1820 or 1825, right after that country's independence from Spain, but did not find any buyers and was dumped at sea in order to avoid customs toll.Friedrich Georg Wieck, ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhodium(III) Compounds
Rhodium is a chemical element with the symbol Rh and atomic number 45. It is a very rare, silvery-white, hard, corrosion-resistant transition metal. It is a noble metal and a member of the platinum group. It has only one naturally occurring isotope: 103Rh. Naturally occurring rhodium is usually found as a free metal or as an alloy with similar metals and rarely as a chemical compound in minerals such as bowieite and rhodplumsite. It is one of the rarest and most valuable precious metals. Rhodium is found in platinum or nickel ores with the other members of the platinum group metals. It was discovered in 1803 by William Hyde Wollaston in one such ore, and named for the rose color of one of its chlorine compounds. The element's major use (consuming about 80% of world rhodium production) is as one of the catalysts in the three-way catalytic converters in automobiles. Because rhodium metal is inert against corrosion and most aggressive chemicals, and because of its rarity, rhodiu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogenation Catalysts
Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically constitutes the addition of pairs of hydrogen atoms to a molecule, often an alkene. Catalysts are required for the reaction to be usable; non-catalytic hydrogenation takes place only at very high temperatures. Hydrogenation reduces double and triple bonds in hydrocarbons. Process Hydrogenation has three components, the unsaturated substrate, the hydrogen (or hydrogen source) and, invariably, a catalyst. The reduction reaction is carried out at different temperatures and pressures depending upon the substrate and the activity of the catalyst. Related or competing reactions The same catalysts and conditions that are used for hydrogenation reactions can also lead to isomerization of the alkenes from cis to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Birch Reduction
The Birch reduction is an organic reaction that is used to convert arenes to cyclohexadienes. The reaction is named after the Australian chemist Arthur Birch and involves the organic reduction of aromatic rings in an amine solvent (traditionally liquid ammonia) with an alkali metal (traditionally sodium) and a proton source (traditionally an alcohol). Unlike catalytic hydrogenation, Birch reduction does not reduce the aromatic ring all the way to a cyclohexane. An example is the reduction of naphthalene in ammonia and ethanol: Reaction mechanism and regioselectivity A solution of sodium in liquid ammonia consists of the intensely blue electride salt a(NH3)xsup>+ e−. The solvated electrons add to the aromatic ring to give a radical anion, which then abstracts a proton from the alcohol. The process then repeats at either the ''ortho'' or ''para'' position (depending on substituents) to give the final diene. The residual double bonds do not stabilize further radical add ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palladium On Carbon
Palladium on carbon, often referred to as Pd/C, is a form of palladium used as a catalyst. The metal is supported on activated carbon to maximize its surface area and activity. Uses Hydrogenation Palladium on carbon is used for catalytic hydrogenations in organic synthesis. Examples include reductive amination, carbonyl reduction, nitro compound reduction, the reduction of imines and Schiff bases and debenzylation reactions. Hydrogenolysis Palladium on carbon is a common catalyst for hydrogenolysis. Such reactions are helpful in deprotection strategies. Particularly common substrate for hydrogenolysis are benzyl ethers: *: Other labile substituents are also susceptible to cleavage by this reagent. Coupling reactions Palladium on carbon is also used for coupling reactions. Examples include the Suzuki reaction and Stille reaction. Preparation A solution of palladium chloride and hydrochloric acid is combined with aqueous suspension of activated carbon. The palladium(II) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Platinum On Carbon
Platinum on carbon, often referred to as Pt/C, is a form of platinum used as a catalyst. The metal is supported on activated carbon in order to maximize its surface area and activity. Uses Catalytic hydrogenation Platinum on carbon is used for catalytic hydrogenations in organic synthesis. Examples include carbonyl reduction, nitro compound reduction, secondary amine production via nitrile reduction, and the production of saturated heterocycles from their respective aromatic compound precursors. Preparation An aqueous solution of activated carbon and chloroplatinic acid is heated on a water bath for a few hours at 50°C, and after cooling, the solution is then made alkaline using sodium carbonate. The chloroplatinic acid is then reduced with hydrazine hydrate; however, this step is sometimes omitted in other preparations. After additional 2 hours of warming, the solution is filtered, washed with distilled water, and dried over calcium chloride to yield the catalyst. Platinum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Platinum Black
Platinum black (Pt black) is a fine powder of platinum with good catalytic properties. The name of platinum black is due to its black color. It is used in many ways; as a thin film electrode, a fuel cell membrane catalyst, or as a catalytic ignition of flammable gases for "self-lighting' gas lamps, ovens, and stove burners. Uses Thin film electrode Platinum black is widely used as a thin film covering solid platinum metal, forming platinum electrodes for applications in electrochemistry. The process of covering platinum electrodes with such a layer of platinum black is called "platinization of platinum". The platinized platinum has a true surface area much higher than the geometrical surface area of the electrode and, therefore, exhibits action superior to that of shiny platinum. Fuel cell membrane catalyst Platinum black powder is used as a catalyst in proton-exchange membrane fuel cells. In common practice, the platinum black is either sprayed using an ultrasonic nozzle or hot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wilkinson's Catalyst
Wilkinson's catalyst is the common name for chloridotris(triphenylphosphine)rhodium(I), a coordination complex of rhodium with the formula hCl(PPh3)3(Ph = phenyl). It is a red-brown colored solid that is soluble in hydrocarbon solvents such as benzene, and more so in tetrahydrofuran or chlorinated solvents such as dichloromethane. The compound is widely used as a catalyst for hydrogenation of alkenes. It is named after chemist and Nobel laureate Sir Geoffrey Wilkinson, who first popularized its use. Historically, Wilkinson's catalyst has been a paradigm in catalytic studies leading to several advances in the field such as the implementation of some of the first heteronuclear magnetic resonance studies for its structural elucidation in solution (31P), parahydrogen-induced polarization spectroscopy to determine the nature of transient reactive species, or one of the first detailed kinetic investigation by Halpern to elucidate the mechanism. Furthermore, the catalytic and organome ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhodium(III) Oxide
Rhodium(III) oxide (or Rhodium sesquioxide) is the inorganic compound with the formula Rh2 O3. It is a gray solid that is insoluble in ordinary solvents. Structure Rh2O3 has been found in two major forms. The hexagonal form adopts the corundum structure. It transforms into an orthorhombic structure when heated above 750 °C. Production Rhodium oxide can be produced via several routes: * Treating RhCl3 with oxygen at high temperatures. * Rh metal powder is fused with potassium hydrogen sulfate. Adding sodium hydroxide results in hydrated rhodium oxide, which upon heating converts to Rh2O3. * Rhodium oxide thin films can be produced by exposing Rh layer to oxygen plasma. * Nanoparticles can be produced by the hydrothermal synthesis. Physical properties Rhodium oxide films behave as a fast two-color electrochromic system: Reversible yellow ↔ dark green or yellow ↔ brown-purple color changes are obtained in KOH solutions by applying voltage ~1 V. Rhodium oxide fil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhodium-catalyzed Hydrogenation
Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically constitutes the addition of pairs of hydrogen atoms to a molecule, often an alkene. Catalysts are required for the reaction to be usable; non-catalytic hydrogenation takes place only at very high temperatures. Hydrogenation reduces double and triple bonds in hydrocarbons. Process Hydrogenation has three components, the unsaturated substrate, the hydrogen (or hydrogen source) and, invariably, a catalyst. The reduction reaction is carried out at different temperatures and pressures depending upon the substrate and the activity of the catalyst. Related or competing reactions The same catalysts and conditions that are used for hydrogenation reactions can also lead to isomerization of the alkenes from cis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcium Chloride
Calcium chloride is an inorganic compound, a salt with the chemical formula . It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with calcium hydroxide. Calcium chloride is commonly encountered as a hydrated solid with generic formula , where ''n'' = 0, 1, 2, 4, and 6. These compounds are mainly used for de-icing and dust control. Because the anhydrous salt is hydroscopic and deliquescent, it is used as a desiccant.Robert Kemp, Suzanne E. Keegan "Calcium Chloride" in Ullmann's Encyclopedia of Industrial Chemistry 2000, Wiley-VCH, Weinheim. Uses De-icing and freezing-point depression By depressing the freezing point of water, calcium chloride is used to prevent ice formation and is used to de-ice. This application consumes the greatest amount of calcium chloride. Calcium chloride is relatively harmless to plants and soil. As a deicing agent, it is much more effective at lower temperat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
