Hydrogenation of metals

E. Rabkin, V.M. Skripnyuk, On pressure hysteresis during hydrogenation of metallic powders, Scripta Mater. 49 (2003) 477-483. 

In the beginning, it seemed like the possible way to solving this problem is by facilitating chemical reactions, primarily hydrogenation of metals. However, decades of intensive search in this direction did not produce expected results. Accordingly, alternative methods began to appear and a number of studies in this field sharply increased. From this perspective, it was important to coordinate and combine efforts of the researchers worldwide as well as create an opportunity for them to periodically meet and discuss their results in order to select the most promising ways and avoid dead ends. 

Tanabe, T., Ninomiya, T., and Izumi, Y. (1970) Asymmetric hydrogenation of C=0 double bond with modified Raney nickel. XV. As5mimetric hydrogenation of metal chelate compounds. Bull Chem. Soc. Jpn. 43,2276. 

Scheme 4 Reaction products derived from the hydrogenation of metal dinitrogen compounds.

Measured heats of hydrogenation of metal-metal bonded complexes (M2(CO)gCp2] are -3.3, +6.3 and -1.5 kcal/mol, for M Cr, Ifo and W, respectively. Further studies of reactions of gas phase transition metal cluster ions with hydrocarbons have been reported. ... 

Operating at high pressure (150 to 200 bar) in the presence of hydrogen, the process is a large consumer of catalyst because of the high amount of metals in the feedstock which deposit on the catalyst. 

The catalytic hydrogenation of ethylene occurs on various metal catalysts, such as nickel, including active or skeletal forms produced by dissolving out... 

Gillan M J 1987 Quantum simulation of hydrogen in metals Phys. Rev. Lett. 58 563... 

Parks E K, Welller B H, Bechthold P S, Hoffman W F, NIeman G C, Pobo L G and Riley S J 1988 Chemical probes of metal cluster structure reactions of Iron clusters with hydrogen, ammonia and water J. Chem. Rhys. 88 1622... 

Gibala R and Hehemann R F (eds) 1984 Hydrogen Embrittlement and Stress Corrosion Craoking (Metals Park, OH American Soceity of Metals)... 

Nickel is a moderately lustrous, silvery metal, and is extensively used in alloys (for example coinage, stainless steel) and for plating where a durable resistant surface is required. It is also used as an industrial catalyst, for example in the hydrogenation of unsaturated organic compounds. It is attacked by dilute aqueous acids but not by alkalis it combines readily with many non-metals on heating. 

Mono and Di-iubstitution Derivatives. The enolic sodium derivative of ethyl acetoacetate (E) is prepared by mixing ethanolic solutions of the ester and of sodium ethoxide. It should not be prepared by the direct action of metallic sodium on the ester, as the reaction is slow and the nascent hydrogen evolved reduces some of the ester to ethyl p4iydroxy- butyrate, CH3CH(OH)CHjCOOEt. 

A convenient form of apparatus, particularly for large classes, is shown in Fig. 84 it is identical with that used for the determination of the equivalent weight of metals by hydrogen evolution. A and H are glass tubes connected together by the rubber tubing J and securely fastened to the board B. The tube A is... 

Iron is a relatively abundant element in the universe. It is found in the sun and many types of stars in considerable quantity. Its nuclei are very stable. Iron is a principal component of a meteorite class known as siderites and is a minor constituent of the other two meteorite classes. The core of the earth — 2150 miles in radius — is thought to be largely composed of iron with about 10 percent occluded hydrogen. The metal is the fourth most abundant element, by weight that makes up the crust of the earth. 

Because of it has great affinity for oxygen, the metal is used as a "getter" in electron tubes. It is also used in photoelectric cells, as well as a catalyst in the hydrogenation of certain organic compounds. 

Common reducing agents are hydrogen in the presence of metallic or complex catalysts (e.g. Ni, Pd, Pt, Ru, Rh), hydrides (e.g. alanes, boranes, LIAIH, NaBHJ, reducing metals (e.g. Li, Na, Mg, Ca, Zn), and low-valent compounds of nitrogen (e.g. NjHj, NjHJ, phosphorus (e.g. triethyl phosphite, triphenyiphosphine), and sulfur (e.g. HO-CHj-SOjNa = SFS, sodium dithionite = Na S O. ... 

A useful alternative to catalytic partial hydrogenation for converting alkynes to alkenes IS reduction by a Group I metal (lithium sodium or potassium) m liquid ammonia The unique feature of metal-ammonia reduction is that it converts alkynes to trans alkenes whereas catalytic hydrogenation yields cis alkenes Thus from the same alkyne one can prepare either a cis or a trans alkene by choosing the appropriate reaction conditions... 

The stereochemistry of metal-ammonia reduction of alkynes differs from that of catalytic hydrogenation because the mechanisms of the two reactions are different The mechanism of hydrogenation of alkynes is similar to that of catalytic hydrogenation of alkenes (Sections 6 1-6 3) A mechanism for metal-ammonia reduction of alkynes is outlined m Figure 9 4... 

Hydrogenation of alkynes may be halted at the alkene stage by using special catalysts Lindlar palladium is the metal catalyst employed most often Hydrogenation occurs with syn stereochemistry and yields a cis alkene... 

The most obvious way to reduce an aldehyde or a ketone to an alcohol is by hydro genation of the carbon-oxygen double bond Like the hydrogenation of alkenes the reac tion IS exothermic but exceedingly slow m the absence of a catalyst Finely divided metals such as platinum palladium nickel and ruthenium are effective catalysts for the hydrogenation of aldehydes and ketones Aldehydes yield primary alcohols... 

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