Why does aluminum chloride with chloroform react with aromatic compounds only?
This reaction is actually a Friedel-Crafts alkylation, where chloroform is the halide (and AlCl3 is the Lewis acid catalyst). Essentially, AlCl3, as a Lewis acid, possesses a low-lying orbital into which it can accept an electron pair. AlCl3 is a very strong Lewis acid, so such a reaction is very favourable. So favourable that it can draw Cl- away from an organic halide R-Cl, giving the very stable AlCl4- and the carbocation R+. This carbocation then attacks an aromatic compound in the manner of electrophilic aromatic substitution. This reaction occurs because R+, an electrophile, readily seeks out the electron-rich unsaturated bonds in aromatic compounds. It will not react with alkanes because they possess no functionalities, and because each atom is electronically saturated (i.e. try drawing a mechanism for attack of R+ upon an alkane, without having any carbon atom part of five bonds at once). On the other hand, addition to an aromatic compound requires only the temporary sacrifice
