Saturated hydrocarbons. See Alkanes

Moreover, the slight differences in reactivity of C—H bonds in alkanes to free radicals lead to indiscriminate attack of the hydrocarbon chains. Improvements in the efficiency and selectivity in the conversion of saturated hydrocarbons under relatively mild conditions is a desirable goal. This objective may be achieved by the selective activation of C—H bonds in alkanes by the use of suitable metal catalysts. The latter condition obtains in the selective microbiological hydroxylation of saturated hydrocarbons (see Section V.A), in which the enzyme probably interacts with the hydrocarbon via metal-catalyzed redox reactions. 

Saturated hydrocarbons are the main constituents of petroleum and natural gas. Mainly used as fuels for energy production they also provide a favorable, inexpensive feedstock for chemical industry [74]. Unfortunately, the inertness of alkanes renders their chemical conversion challenging with respect to selectivity. Clearly, the development of new and improved methods for the selective transformation of alkanes belongs to the central goals of catalysis. Iron-catalyzed processes might be a smart tool for such transformations (for reviews see [75-77]). 

The simplest member of the saturated hydrocarbons, which are also called the alkanes, is methane (CH4). As discussed in Section 14.1, methane has a tetrahedral structure and can be described in terms of a carbon atom using an sp-J hybrid set of orbitals to bond to the four hydrogen atoms (see Fig. 22.1). The next alkane, the one containing two carbon atoms, is ethane (C2H6), as shown in Fig. 22.2. Each carbon in ethane is surrounded by four atoms and thus adopts a tetrahedral arrangement and sp3 hybridization, as predicted by the localized electron model. 

It can be seen from the graph that the equilibrium products at temperatures below 500°C are mainly alkanes (also known as paraffins or saturated hydrocarbons), with the equilibrium giving roughly a 2 1 ratio of isopentane to normal pentane. As the temperature is increased from 500°C to 600°C, there is increased formation of alkene compounds (also known as olefins). At 700°C, we see increased formation of cyclo-pentene and of dienes, and above 800°C dienes are the favored product. 

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