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Source: http://www.mhhe.com/physsci/chemistry/carey/student/olc/graphics/carey04oc/ref/ch12overview.html

Image Credits: MHHE

In the electrophilic aromatic substitution attack of Benzene by the nucleophile, as shown in the figure, nucleophile attacks hydrogen of the intermediate, instead of attacking the positive charge distributed ring; leading to substitution reaction.

Bezene's closed shell of six pi electrons is said to give it an extra stability (resonance energy)$_1$, but it is not clear and precise in the explanation of how the electric attraction is overcome by this another tendency which is described. So, the question is, how is this electrostatic attraction towards positive ring overcome by other tendency of stability?

$_1$ Organic Chemistry 11e by Solomons, Fryhle, Snyder, pg.671.

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The positive charge, instead of being localized, is actually delocalized throughout the ring because of resonance, making the charge shared between three carbons, lessening the ability for the nucleophile to attack the positive charge.

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  • $\begingroup$ But, it is of high probability for the nucleophile to get attracted towards a less positively charged ring than the neutral hydrogen. $\endgroup$ – Immortal Player Oct 12 '16 at 12:42
  • $\begingroup$ @ImmortalPlayer The problem is that addition breaks the $\pi$-system created by the benzene ring. The $\pi$-system stabilizes the benzene. $\endgroup$ – DHMO Oct 12 '16 at 12:44
  • $\begingroup$ @ImmortalPlayer I think I'll leave it to someone who knows more than me. $\endgroup$ – DHMO Oct 12 '16 at 12:45
  • $\begingroup$ It seems that, I need to add more description, I will be back soon. Thank you for the time. $\endgroup$ – Immortal Player Oct 12 '16 at 12:47
  • $\begingroup$ I might need to understand QM first, before any trial of thinking into Chem. $\endgroup$ – Immortal Player Oct 12 '16 at 13:17

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