Question

Limitations of Fridal craft reaction?

Answer 1

73093 "Limitations of Friedel-Crafts Reactions"

① In alkylation carbocation can rearrange to more stable form (irrespective of whether it is formed from alkyl halide, alkene or alcohol).

Rearrangements do not occur in Friedel-Craft acylations. The acylum ion is resonance stabilized, so there is no need for it to rearrange.

② If the groups present are -NH₂, -NHR, -NR₂ or -OH, Friedel-Crafts reactions give very poor yields.

③ Aryl and vinylic halides can't be used as halide component because of the difficulty in producing the corresponding carbocations:

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④ Poly alkylations take place frequently during alkylation reactions but in case of alkylation no such difficulty arises. Synthetic applications of Friedel-Craft reactions:

a)

b)

c)

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