Question

Friedel-Crafts Alkylation is a special type of EAS reaction. The reaction involves the use of highly caustic and dangerous chemicals. Why are these conditions necessary? What conditions would be required if these chemicals were not used?

Answer 1

I am not very confident about the reasons. However just to help you writing whatever I know. Please let me know if you need anything else. I will dig it out.

Friedel-Crafts Alkylation reaction needs strong lewis acid to polarize the alkyl halide, so as to create a carbocation/electrophile to attack aromatic ring. In the absence of lewis acid the polarization of alkyl halide is weak and the polarisation of alkyl halide will not be effective for the electrophilic attack on aromatic ring.

Not sure about the conditions in the absence of the lewis acid.

Some guess

1) In the absence of lewis acid, generation of carbocation which will attack aromatic ring is not possible or the reaction will be very slow or will not happen at all.

2) Tertiary carbocations are easy to generate than primary. So use of tertiary halide is one option to increase the rate of reation in the absence of lewis acid.

3) We basically need to create carbocation which will attack aromatic ring. So other option is to use alcohol and bronsted acid to generate carbocation as shown below.