Halogenation higher alkanes

Chlorination of most of higher alkanes gives a mixture of isomeric monochloro products as well as more highly halogenated compounds. 

Up to now, we have limited our discussions to the halogenation of methane. Beginning our study with such a simple compound allowed us to concentrate on the thermodynamics and kinetics of the reaction. Now we consider halogenation of the higher alkanes, meaning those of higher molecular weight. 

As we might expect, halogenation of the higher alkanes is essentially the same as the halogenation of methane. It can be complicated, however, by the formation of mixtures of isomers. 

Effects of Halogens- A study of the partial catalytic oxidation of CH4 over palladium sponge catalysts by Cullis et al. yielded some information quite relevant to its use for complete oxidation in air pollution control. They found that (1) the presence of higher alkanes or of partial oxidation products of methane, HCHO and CH3OH, retard the overall oxidation of the CH4 (2) the wide variety of halomethanes studied retarded the oxidation of CH4 to different extents and (3) some chloromethanes increased the production of HCHO with high selectivity. They attributed the latter to the modification of the elecuonic properties of the catalyst surface by the chloromethane to inhibit the further oxidation of the HCHO. 

Inhibition of detonation. Chemical additives can have a large effect on experimentally observed ignition delay times. Small amounts of NO2, N2O, H2, or higher alkanes can significantly reduce the induction time in CH4-O2 and CH4-air mixtures (4,9,42,46,30-33). Conversely, halogenated species have been shown (36,37) to increase the Induction time in fuel-02 mixtures. Since the induction time is a critical factof in determining the detonability of fuel-oxidizer... 

Higher alkanes react with halogens by the same kind of chain mechanism as those that we have just seen. Ethane, for example, reacts with chlorine to produce chloroethane (ethyl chloride). The mechanism is as follows ... 

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