Hydrogen as a reducing agent

Hydrogen as a reducing agent oxygen as an oxidizing agent. 

In most of our studies we have used hydrogen as a reducing agent and employed Raney nickel as catalyst, but in view of the low hydrogen uptake observed with mature catalyst some experiments were performed in the absence of hydrogen and these have yielded very encouraging results. 

Zhang, H. Hu, M. Cai, M. Reductive coupling of disulfides and diselenides with alkyl halides catalyzed by a silica-supported phosphine rhodium complex using hydrogen as a reducing agent. J. Chem. Res. 2013, 645-647. 

As the above redox potentials indicate, only in the presence of very powerful oxidising agents does hydrogen peroxide behave as a reducing agent. For example ... 

A variation of the classical reductive amination procedure uses sodium cyanoboro hydride (NaBH3CN) instead of hydrogen as the reducing agent and is better suited to amine syntheses m which only a few grams of material are needed All that is required IS to add sodium cyanoborohydride to an alcohol solution of the carbonyl compound and an amine... 

Reagents, such as tri alkyl aluminums (90) and sodium benzophenone (109), are quite useful as reducing agents. Alkyl aluminums have been used to synthesize Cr(CO), Mo(CO), and W(CO) in high yields (90). In one case, hydrogen was used effectively as a reducing agent in petroleum ether solvent (110,111). 

The available studies indicate that diimide has been used as a reducing agent for the preparation of HNBR. It has been used mainly as an alternative for hydrogenation of nitrile rubber latex. The use of diimide to hydrogenate low-molecular weight olefines is well known in the organic literature [93]. Diimide can be conveniently generated in situ by thermal treatment of solutions of p-tolu-enesulfonyl hydrazide or oxidation of hydrazine. 

Using data in Appendix 1, estimate the temperature at which Fe203 can be reduced to iron, using hydrogen gas as a reducing agent (assume H20(g) is the other product). 

Like ammonia, hydrogen sulfide (oxid. no. S = —2) can act only as a reducing agent when it takes part in redox reactions. Most often the H2S is oxidized to elementary sulfur, as in the reaction... 

Reaction (2) is often preferred because of the hazard of unconsumed chlorine from Reaction (1) reacting explosively with hydrogen commonly used as a reducing agent. 

The main gaseous product is the hydrogen. Carbon can be either sequestered or used as a material commodity under less severe CO2 restraints. It can also be used as a reducing agent in metallurgical processes. From the point of view of carbon sequestration, it is easier to separate, handle, transport, and store solid carbon than CO2 [5]. 

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