Friedel-Crafts alkylation with carbocation precursors

SO on, loss of a proton leads to aromatization, completing the substitution reaction to form the new carbon bond in 159. Electrophilic aromatic substitution with alkyl carbocations is called Friedel-Crafts alkylation. It was reported by Friedel and Crafts in 1877. The carbocation precursor can be an alkene, an alcohol, or an alkyl halide. 

Friedel-Crafts alkylations can be carried out with any starting material that functions as a precursor to a carbocation, such as an alcohol or alkene (Sections 9-2 and 12-3). 

Apart from the alkyl halide-Lewis acid combination, two other sources of carbo-cations are often used in Friedel-Crafts reactions. Alcohols can serve as carbocation precursors in strong acids such as sulfuric or phosphoric acid. Alkylation can also be effected by alcohols in combination with BF3 or A1C13.37 Alkenes can serve as alkylating agents when a protic acid, especially H2S04, H3P04, and HF, or a Lewis acid, such as BF3 and A1C13, is used as a catalyst.38... 

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