Beiträge zum Reaktionsmechanismus bei der Friedel‐Craftsschen Reaktion

Alkylation and the Action of Aluminum Halides on Alkylbenzenes.

“…The 1,2,4,5-tetraisopropylbenzene is reported from the following reactants: (1) benzene, isopropyl alcohol, and concentrated sulfuric acid (48); (3) benzene, propylene, and concentrated sulfuric acid, aluminum chloride, or hydrogen fluoride (39, 8, 14a); (3) benzene, isopropyl chloride, and aluminum chloride (88). In these reactions, aluminum chloride, hydrogen fluoride, and concentrated sulfuric acid all appear to give the same tetraalkylbenzene.…”

“…From extensive conductivity studies of the system benzene-ethyl bromide-aluminum bromide, Wertyporoch (88) concludes that "the classical Friedel-Crafts reaction is dependent on the formation of an ionized ternary complex. In the ethyl bromide molecule, the union between C2H5 and Br is loosened through salt formation, and likewise the carbonhydrogen bond in the benzene combined in the cation, and stabilization can take place through the formation of ethylated benzenes with the elimination of hydrogen bromide."…”

Carbocations in Superacid Systems

“…The existence of alkyl cations in systems containing alkyl halides and Lewis acids has been inferred from a variety of observations, such as vapor pressure depressions of CH 3 Cl and C 2 H 5 Cl in the presence of GaCl 3 , 82 conductivity of AlCl 3 in alkyl chlorides, 83 and conductivityof alkyl fluorides in BF 3 , 84 as well as the effect of ethyl bromide on the dipole moment of AlBr 3 . The existence of alkyl cations in systems containing alkyl halides and Lewis acids has been inferred from a variety of observations, such as vapor pressure depressions of CH 3 Cl and C 2 H 5 Cl in the presence of GaCl 3 , 82 conductivity of AlCl 3 in alkyl chlorides, 83 and conductivityof alkyl fluorides in BF 3 , 84 as well as the effect of ethyl bromide on the dipole moment of AlBr 3 .…”

The Friedel-Crafts Syntheses.

“…Higher alkyl halides react similarly to the simple halides. Propyl (144, 446), butyl (167,163, 20, 291a), and amyl (119, 144) halides react to yield, largely, branched alkyl substances. Generally, regardless of the configuration of the alkyl halide, the final product contains an alkyl group of the highest possible branching (144).…”

“…There is no demonstrable complex formation between the aluminum halide and the alkyl halide or benzene, if benzene is being alkylated (268, 212a, 269). However, there is strong evidence that a ternary complex may be formed in which the benzene, aluminum halide, and alkyl halide take part (373,455,446). The aluminum halide retains its activity, so that a small quantity of metallic halide may be used to alkylate large quantities of many benzene derivatives.…”