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Friedel–Crafts alkylations can be reversible. Although this is usually undesirable it can be exploited; for instance by facilitating transalkylation reactions. [10] 1,3-Diisopropylbenzene is produced via transalkylation, a special form of Friedel–Crafts alkylation. It also allows alkyl chains to be added reversibly as protecting groups.
The Friedel–Crafts reaction can be performed either as an acylation or as an alkylation. Often, aluminium trichloride is used, but almost any strong Lewis acid can be applied. For the acylation reaction a stoichiometric amount of aluminum trichloride is required.
Nucleophilic alkylating agents can displace halide substituents on a carbon atom through the SN2 mechanism. With a catalyst, they also alkylate alkyl and aryl halides, as exemplified by Suzuki couplings. The Kumada coupling employs both a nucleophilic alkylation step subsequent to the oxidative addition of the aryl halide (L = Ligand, Ar = Aryl).
The Friedel-Crafts alkylation process involves chlorination of n-paraffins to monochloroparaffins followed by alkylation of benzene using aluminum chloride (AlCl 3) catalyst. This method is one of the oldest commercial routes to LABs. Each process generates LAB products with distinct features.
In step three dihydrogen is split off with rearomatisation to the biaryl compound. In the arenium ion mechanism one reaction partner is ... Friedel-Crafts alkylation
Clemmensen reduction conditions are particularly effective at reducing aryl [4]-alkyl ketones, [5] [6] such as those formed in a Friedel-Crafts acylation. The two-step sequence of Friedel-Crafts acylation followed by Clemmensen reduction constitutes a classical strategy for the primary alkylation of arenes.
In the case of the Friedel–Crafts alkylation, the reaction can be broken into three steps as follows: [1] The alkyl halide reacts with the strong Lewis acid to form an activated electrophile composed of the tetrachloroaluminate ion and the alkyl group.
The concerted mechanism of this step is similar to the mechanisms of the Baeyer–Villiger oxidation [6] and Criegee rearrangement reactions, and also the oxidation step of the hydroboration–oxidation process. [7] In 2009, an acidified bentonite clay was proven to be a more economical catalyst than sulfuric acid as the acid medium.