Palladium-hydrogen

Platinum and palladium are the most common catalysts for alkene hydrogenations. Palladium is normally used as a very fine powder supported" on an inert material such as charcoal (Pd/C) to maximize surface area. Platinum is normally used as PtC, a reagent called Adams catalyst after its discoverer, Roger Adams. 

Hydrogen peroxide, Palladium catalyst See Hydrogen peroxide Hydrogen, Palladium catalyst... 

Nitryl fluoride Non-metals Oxygen (Gas) Hydrogen Palladium(II) oxide Hydrogen Xenon hexafluoride Hydrogen... 

Hydrogen peroxide, Hydrogen, Palladium catalyst, 4477 3-Methyl-2-penten-4-yn-l-ol, 2384... 

A method for the conversion of unsaturated aliphatic aldehydes to saturated aldehydes is a gentle catalytic hydrogenation. Palladium is more selective than nickel. Hydrogenation over sodium borohydride-reduced palladium in methanol at room temperature and 2 atm reduced crotonaldehyde to butyralde-hyde but did not hydrogenate butyraldehyde [57]. Nickel prepared by reduction with sodium borohydride was less selective it effected reduction of crotonaldehyde to butyraldehyde but also reduction of butyraldehyde to butyl alcohol, though at a slower rate [57]. Hydrogenation of 2,2,dimethyl-... 

The reduction of carbazole nitro groups to the primary amines is straightforward stannous chloride, tin-hydrochloric acid, iron-hydrochloric acid" hydrogen-palladium/charcoal," hydrogen-nickel,hydrazine-palladium,and hydrazine-nickeP have all been employed. 3,6-Dichloro-l,8-dinitrocarbazole was partially reduced with sodium hydrogen sulfide to give l-amino-8-nitro-3,6-dichloro-carbazole. ... 

Iodine at the N-alkylcarbazole 3-position has been reductively removed with lithium aluminium hydride - and hydrogen-Raney nickel, and bromine at the same position has been removed with lithium-tcrt-butanol. Hydrogen-nickel at 600 psi has also been used to hydrogenolyze carbazole carbon-bromine bonds, and hydrogen-palladium/charcoal at 200°C to remove a 1-chlorine. ... 

Presumably a 2 -oxy-2-aminobiphenyl is intermediate in the conversion of 292 with ammonia at 135°C to 1,3,6,8-tetranitrocarbazole. The p-benzoquinones 293 (R = H, Me or OMe) gave 294 on reduction with hydrogen-palladium-acid and 295 on reduction with sulfur dioxide. Compound 294 on oxidation with iron(III) chloride and compound 295 on reduction with hydrogen-nickel produced the 3-hydroxycarbazoles 296. ... 

The solution of hydrogen in palladium must be considered as a different type of alloy system, because the hydrogen cannot replace palladium in the lattice structure. The fall in susceptibility to zero at a hydrogen-palladium ratio of 0.55 suggests that all the electrons of the hydrogen atoms enter the 4d palladium levels (11). 

These substances, like most compounds with peroxide (O—O) bonds, may explode violently and unpredictably. Therefore ozonizations must be carried out with appropriate caution. The general importance of these reactions derives not from the ozonides, which usually are not isolated, but from their subsequent products. The ozonides can be converted by hydrolysis with water and reduction, with hydrogen (palladium catalyst) or with zinc and acid, to carbonyl compounds that can be isolated and identified. For example, 2-butene... 

H. Palladium. Palladium (mp 1,SS2°C), is soft and ductile but work-hardens. At elevated temperatures, the diffusion of hydrogen through palladium is rapid, which forms the basis of a method for the purification of hydrogen. The best performance is obtained from a palladium-silver alloy containing about 18% silver because, unlike pure Pd, this alloy does not undergo a phase transition in the presence of hydrogen. Palladium is not as inert as platinum and is attacked by sulfuric and nitric acids. 

Siantar, D.P., Schreier, C.G., Chou, C., and Reinhard, M., Treatment of 1,2-dibromo-3-chloropropane and nitrate-contaminated water with zero-valent iron or hydrogen/palladium catalysts, Water Res., 30(10), 2315-2322, 1996. 

As important as it is, the hydrogen-palladium system is rather limited in its application. For this reason, other electronic materials that could operate on the same principle have been investigated. Organic semiconductors proved to be most useful in that respect. 

The 2-deoxy function may be regenerated from the 2-halo derivatives by reduction with tributyl stannic hydride, NiC /NaBH, or hydrogen/palladium on charcoal. The latter should be carried out in the presence of base in order to quench the resulting acid. Another method following the same concept is the oxyselenation-deselenation of glycals [13] ... 

Hydrogen peroxide, Hydrogen, Palladium catalyst, 4471 3-Methyl-2-penten-4-yn-l-ol, 2378 l,Ll-Tris(azidomethyl)ethane, 1931 Tris(hydroxymethyl)nitromethane, 1658 See CATALYTIC NITRO REDUCTION PROCESSES, HYDROGEN TRANSFER... 

Section 6 describes the use of the kinetic theory for studying physicochemical mechanics problems. An example of the theory is used to explain the observed properties for hydrogen-palladium systems. It is also used to self-consistently connect the local adsorption and diffusion characteristics of hydrogen atoms with the deformations within the metal membrane. 

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