{"id":9326,"date":"2024-02-25T00:28:46","date_gmt":"2024-02-25T00:28:46","guid":{"rendered":"https:\/\/chemistryscore.com\/?page_id=9326---03d0050a-4d9c-462f-8dc7-f132379f5d41"},"modified":"2024-02-25T00:28:46","modified_gmt":"2024-02-25T00:28:46","slug":"friedel-crafts-alkylation-r-x-plus-catalyst","status":"publish","type":"post","link":"https:\/\/chemistryscore.com\/friedel-crafts-alkylation-r-x-plus-catalyst\/","title":{"rendered":"Friedel Crafts alkylation [R-X plus catalyst]"},"content":{"rendered":"\t\t
In\u00a0Friedel-Crafts alkylation<\/strong>, treatment of\u00a0benzene<\/strong>\u00a0with an\u00a0alkyl halide<\/strong>\u00a0and a\u00a0Lewis acid<\/strong>\u00a0(AlCl3<\/sub>\u00a0or FeCl3<\/sub>) forms an\u00a0alkylbenzene<\/strong>. This reaction is an\u00a0alkylation<\/strong>\u00a0because it results in the transfer of an\u00a0alkyl group<\/strong>\u00a0from one atom to another (from X to benzene).<\/p> <\/p> The\u00a0Friedel-Crafts alkylation<\/strong>\u00a0forms new carbon-carbon bonds by the installation of an alkyl group on an aromatic ring.<\/p> The reactivity of alkyl halides increases with the polarity of the carbon-halide bond in the order:\u00a0RI < RBr\u00a0< RCl < RF<\/strong><\/p> Typical\u00a0Lewis acids are\u00a0FeCl3<\/sub><\/strong>,\u00a0AlCl3<\/sub><\/strong>, and\u00a0AlBr3<\/sub><\/strong>.<\/p> Step 1.<\/strong>\u00a0Alkyl halide activation and formation of\u00a0carbocation<\/strong>\u00a0which is an excellent electrophile<\/p> Step 3<\/b>. Deprotonation of sigma complex to restore aromaticity<\/p> <\/p> This is an example for\u00a0secondary<\/strong>\u00a0and\u00a0tertiary halides<\/strong>\u00a0but with primary halides, it is slightly different.\u00a0Primary alkyl halides<\/strong>\u00a0are not converted into carbocations since\u00a0primary carbocations<\/strong>\u00a0are extremely high in energy. In this case, the electrophilic agent is presumed to be a\u00a0complex<\/strong>\u00a0between alkyl halide and catalyst.<\/p> Friedel-Crafts alkylation can be carried out with any starting material that functions as a precursor to a carbocation, such as\u00a0alcohol<\/strong>\u00a0or\u00a0alkane<\/strong>. And also can be used to fuse a new ring onto the benzene nucleus by an\u00a0intramolecular Friedel-Crafts alkylation<\/strong>.<\/p>Friedel Crafts alkylation [R-X plus catalyst] Explained:<\/h2>
Mechanism of Friedel-Crafts alkylation<\/h3>
Step 2<\/b>. Nucleophilic attack of benzene to carbocation and form an intermediate sigma complex<\/p>