Hydrogenating agents

Dia ene deductions. Olefins, acetylenes, and azo-compounds are reduced by hydrazine in the presence of an oxidizing agent. Stereochemical studies of alkene and alkyne reductions suggest that hydrazine is partially oxidized to the transient diazene [3618-05-1] (diimide, diimine) (9) and that the cis-isomer of diazene is the actual hydrogenating agent, acting by a concerted attack on the unsaturated bond ... 

Seaetms.—1. By the action of reducing or hydrogenating agents, as zinc and hydrochlorio acid, sulphuretted hydrogen, acetic acid and iron, or potassic acsenite, nitrobenzol is con verted into aniline —... 

Several years ago, one of the authors found that nickel, platinum, and some other hydrogenating agents, when deposited on fresh synthetic silica-alumina cracking catalyst, made a new catalyst that would isomerize paraffin and naphthene hydrocarbons in the presence of hydrogen at elevated pressures and nominal temperatures. Table I shows some early typical results calculated from mass spectrometer analyses of the products obtained by passing methyl cyclopentane, cyclohexane, and n-hexane over a catalyst composed of 5% nickel in silica-alumina at the indicated reaction conditions. Isomerization of a number of other hydrocarbons has also been studied and reported elsewhere (2). 

Hydrazine actually has been used as a hydrogenating agent for over sixty years, but it was not until the 1960 s that the diimide intermediate in such reactions was recognized. 

Further applications of the silane/acid (i. e. 720/trifluoroacetic acid) system include reductions of steroidal substrates95,96 Another notable variant is the use of methylpolysiloxane (757)88 97 especially in presence of bis(dibutylacetoxytin)-oxide (DIBATO)97 as hydrogenating agent via this method benzophenone (135) yields diphenylmethanol (138) (Scheme 16). Under hydrosilylation-like conditions... 

Mannich base from Hydrogenation agent (Reference)... 

Isomerisation of olefins catalysed 11 by palladium and other transi- (34) tion-metal complexes Hydrogenation reaction with 10 cobalt carbonyl hydride as a (29) hydrogenation agent 7r-Complex adsorption in hydrogen 27 exchange on Group VIII transi- (45) tion metal catalysts... 

When two double bonds become conjugated, the conjugated system attaches itself to the catalyst—perhaps through a temporary expansion of the coordination sphere (10, 11), This addition is irreversible, but the addition compound is split by the hydrogenating agent shown below on... 

There are numerous examples in which H20 and CO were used as hydrogenating agent, taking advantage of the water-gas shift equilibrium, which generates H2 and C02 from the water and carbon monoxide feedstock (cf. Section V,A). 

Use Powder metallurgy, production of pure hydrogen (can contain 1800 cc (STP) H/cc of hydride), production of foamed metals, solder for metal-glass composites, electronic getter, reducing atmosphere for furnaces, hydrogenation agent, refractories. 

As already discussed in Sects. 6.4.5 and 6.4.6, recent developments have stimulated interest in using supported Au catalysts as active oxidation and hydrogenation agents, respectively. H2/O2 mixtures have also been used for the oxidation of propene to propene oxide using Au catalysts [169], and it is considered that a surface hydroperoxy species may be formed as the oxidant (see Sect. 6.4.5) [41,112,470]. Theoretical calculations [470] predicted that formation of H2O2 should be promoted by gold surfaces. 

In the case of thiourea it was suggested that the free radical formed by a reaction with water, (NH2)2CS"-> (NH2)2CSH-l-OH", acts as a hydrogenating agent toward polyethylene oxide (Charlesby et al., 1965) however, an electron-transfer mechanism from (NH2)2CS" cannot be excluded. 

The choice of a reducing agent for the preparation of aminoisoxazoles is not always obvious because mild hydrogenating agents, which do not affect the isoxazole... 

The salt Li[AlH4] is a widely used reducing and hydrogenating agent it is obtained as a white solid by reaction 12.23 or 12.24, and is stable in dry air but is decomposed by water (equation 12.25). 

Finally silicon can be etched in fluorocarbon plasmas (e.g., CF4). The addition of oxidation (oxygen) or reducing (hydrogen) agents to these plasmas has been used to control polymer formation and thereby affect the etch rate and selectivity. Fig. 43... 

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