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Explain seconds steps of general electrophilic substitution reaction of benzene. |
Answer» Solution :In first slow step, electrophiles are attaches with benzene and form `-sigma`-complex. `sigma`-complex loses proton. Proton is donated to the negative ion form in steps which gives electrophilic `sigma`-complex, and gives substitution product. <BR>  `A^(-) + H^(+) rarr H^(+)A^(-) + "Catalyst"` `FeCl_(4)^(-) + H^(+) rarr HCl + FeCl_(3) + C_(6)H_(5)Cl` `FeBr_(4)^(-) + H^(+) rarr HBr + FeBr_(3) + C_(6)H_(5)Br` `AlCl_(4)^(-)+ H^(+) rarr HCl+ AlCl_(3) + C_(6)H_(5)E` all carbons are `SP^(2)` in substituted product. Aromatic character is possessed by substituted product. `sp^(3)` carbon is converted into `sp^(2)` when substitution product is formed. Second step is not rate determining because it is fast step. At the end of second step, product is formed by attachment of electrophile in place of H present in main compound. So mechanism is of electrohilic substitution TYPE. |
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