Carbonic acids, hydrogen bonding cooperativity

In the context of alkanes, hydrogenolysis is the breaking of C—C bonds by the action of hydrogen, leading to alkanes of lower molar mass. It is not a reaction that is deliberately practised on a large scale, but it is a parasitic reaction that occurs in parallel with other useful reactions of alkanes to be considered in the next chapter. In order to learn how to avoid or minimise it, it becomes necessary to find out as much as possible about it, and this is most easily done with molecules containing only two to four carbon atoms. Alkanes can also be cracked by an acid-catalysed reaction on solid acids or acidic supports, but in this chapter we are solely concerned with reactions that proceed on purely metallic sites the cooperation of metallic and acidic sites in petroleum reforming will be briefly considered in Chapter 14. 

The catalytic effect of Ir4(CO)i2 on the methanation reaction is notoriously enhanced by the presence of strong Lewis acids, probably due to a cooperative activation of the carbon-oxygen bond. Thus the catalysis with Ir4(CO)i2 in a NaCl/AlCl3 melt converts at very reasonable rate carbon monoxide and hydrogen into light hydrocarbons, primarily ethane, without producing oxygenated compounds. 

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