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Explain which type of mechanism is involved in alkylation of benzene ? |
Answer» Solution :Alkylation of benzene means attachment of ALKYL `(R^(+))` group with hydrogen of benzene by following in reaction.  The carbocation FORM during the alkylation of benzene is attached in two steps. Step -1 This step is slower. In which carbocation `overset(+)(C)H_(3)//CH_(3)overset(+)(C)H_(2)` attaches to the benzene ring and form `sigma`-complex. Step-2 : In this second step `sigma`-complex loses `H^(+)` and form alkyl benzene. This step is fast and form SUBSTITUTION product.  In the FIRS step of this reaction electrophiles are added and stable `sigma`-complex form by resonance. The resonance forms of `sigma`-complex A, B, C and hybride structure (D) are as follows.  Second fast steps : `sigma` -complex is not aromatic in nature, the intermediate is unstable. So, in second steps, it immediately loses its `H^(+)` and form stable aromatic alkyl benzene. 
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