Reaction with hydrogen gas

Alkanes are already saturated, ie all their C-H bonds are single sigma bonds, and so they do not have any capacity to take up hydrogen. In alkenes the double bond can be opened up to add on a molecule of hydrogen gas H2, and the corresponding alkane is formed. 

The reaction will be helped if the two gases are mixed and passed over a suitable catalyst, e.g. hot nickel (look back at Section 5.3.5). 

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About 70% of the western world s supply of nickel comes from iron and nickel sulfide ores that were brought close to the surface nearly 2 billion years ago by the violent impact of a huge meteor at Sudbury, Ontario. The ore is first roasted (heated in air) to form nickel(II) oxide, which is reduced to the metal either elec-trolytically or by reaction with hydrogen gas in the first step of the Mond process ... 

Metal ion discharge, chemical identity of adsorbed intermediates, 38 19-20 Metal ion-exchanged zeolites, 31 13 Metallacycle mechanism, 41 323-324 Metallathiabenzenes formation of, 42 421 reaction with hydrogen gas, 42 420 Metallic catalysts, 27 3 see also specific catalysts... 

The use of hydrogen gas in hydrogenation reactions is often considered inconvenient, because of the necessity to carry out the reactions in closed vessels in an oxygen-free atmosphere. Additionally, reactions with hydrogen gas often require high pressure and the use of autoclaves. 

Fulleranes by Direct Reaction with Hydrogen Gas at Elevated Conditions... 

The processing of nickel oxide ores is illustrated by the sulfuric acid leaching of nickeliferous laterites and the precipitation of high-purity nickel and cobalt powder by reaction with hydrogen gas giving ammonium sulfate as by-product. This process is in use at Moa Bay, Cuba. 

The hydrogen in lignin is increased by a spectrum of reactions ranging fiom catalytic reaction with hydrogen gas, (g), to reaction with sodium borohydride, NaBH.,. 

Yoo S, Dregia S, Akbar SA, Rick H, Sandhage KH. Kinetic mechanism of T1O2 nanocarving via reaction with hydrogen gas. J Mater Res 2006 21 1822-9. 

In this process, the metal is catalytic in that it serves as a template for reaction with hydrogen gas and the formation of two new a-covalent C-H bonds. The catalyst facilitates hydrogen transfer to the alkene, but it is regenerated when the cycle is complete. Therefore, only a catalytic amount of the metal is required. The mechanism outlined in Figure 19.1 is used to explain the reduction of 1-heptene to heptane with hydrogen gas and nickel or certain other metals. 

On reaction with hydrogen gas with a platinum catalyst, ribose (Problem 5.54) is converted into ribitol. Is ribitol optically active or inactive Explain. 

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