Outline the mechanistic steps involved in the arenium ion mechanism for aromatic electrophilic substitution. Draw the energy profile diagram for the proposed mechanism. Give one evidence in support of the proposed mechanism.

I can solve the first two questions but I got confused about what the last question exactly asking for. Any help will be appreciated.


You say you've already drawn the energy profile diagram for your proposed mechanism , now you want to make sure that your reaction mechanism proceeds through the most stable transition state , ( Least activation energy ) and therefore , on the energy profile diagram , the peak occuring at the transition state should not be too high .Also you wanna make sure that your final products have energies lesser than the reactants , because in that case , your $\Delta H$ would be $-ve$ and from the equation $\Delta G=\Delta H-T\Delta S $, there would be a greater chance your reaction moves forward.enter image description here

You also should have a look at this

  • $\begingroup$ Thanks But the last question that I am asking for carries only one mark. How can I answer it precisely? $\endgroup$
    – Sanu_012
    Feb 25 '18 at 6:13
  • $\begingroup$ @Sanu_012 You could explain it from the energy diagram , like I have , or you could point out in the mechanism that the carbocation formed during the mechanism is resonance stabilised and hence favours the forward reaction. $\endgroup$
    – Tanuj
    Feb 25 '18 at 6:19
  • $\begingroup$ Thanks a lot. I gonna explain it in the carbocationic way. It is worth one mark. $\endgroup$
    – Sanu_012
    Feb 25 '18 at 6:23
  • 1
    $\begingroup$ I don't see how this is supposed to answer the question... $\endgroup$
    – Mithoron
    Feb 25 '18 at 17:55

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