Syntheses of Wurtz type

A Wurtz synthesis consists of removal of halogen from an alkyl halide by means of an alkali metal, with linkage of two alkyl groups to form a longer alkyl chain, thus  

Fittig applied this reaction to the aromatic series, combining an alkyl with an aryl halide. 

In the aliphatic series the results are useful only for linkage of two identical halides, i.e., when R = R the smooth course of the Fittig reaction (see below) depends on the facts that aromatic halides react much faster than alkyl halides with the metal and, further, that arylsodiums react faster than alkylsodiums with an alkyl halide (for justification of these statements see the elementary textbooks). 

Nowadays the Wurtz synthesis is seldom used, but it still provides a method for preparing very long-chain carbon compounds of defined molecular weight. 

Hell and Hagele310 prepared hexacontane as follows When triacontyl iodide (10 parts) is heated with potassium (1 part) at 130-140°, the reaction appears to be complete after 2 h. Working up is very laborious the product is boiled successively with water, ethanol, light petroleum, and glacial acetic acid, then recrystallized from benzene, and again boiled with light petroleum until finally hexacontane remains as an indistinctly crystalline, colorless powder of m.p. 101-102°. 

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