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Mono-nitration reaction

Hi, I tried to answer this question based wholly on the concepts of inductive effects. But haven't gotten anywhere with it. I would appreciate any help regarding these questions:

  1. What condition makes a compound to give meta product(instead of ortho or para)?

  2. I know there is some flaw with my approach, so what is the correct way to do it?

  3. Can this condition be applied to other compounds as well, or is it just for aromatic compounds?

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closed as too broad by airhuff, Todd Minehardt, Jon Custer, Tyberius, M.A.R. Jan 8 at 1:20

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ Which of these compounds will protonate under nitration conditions? Will this change the directing properties? $\endgroup$ – Waylander Jan 6 at 20:27
  • $\begingroup$ @Waylander As far as I know, all these compounds are ortho-para directors. So, I am really confused how do they give more amounts of meta product. $\endgroup$ – The Jokster Jan 6 at 20:31
  • $\begingroup$ Would aniline protonate under std nitration conditions of sulfuric acid/nitric acid? Would the anilinium cation still be o/p directing? $\endgroup$ – Waylander Jan 6 at 20:46
  • $\begingroup$ @Waylander Sorry, but I don't know. Hence the question. $\endgroup$ – The Jokster Jan 6 at 20:51
  • $\begingroup$ The answer is it is no longer a strong director once it is protonated so you get a fair bit of meta. $\endgroup$ – Waylander Jan 6 at 20:55
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The answer to the question is (1) Aniline.

This occurs because under standard strongly acidic nitrating conditions (typically cH2SO4/HNO3) the aniline NH2 is protonated removing the ability of nitrogen lone pair to donate any electrons. Consequently the electron-withdrawing polar effect makes it m-directing. Some p-nitroaniline is formed because there is a small amount of the aniline freebase in equilibrium with the anilinium, but that is much more reactive than the anilinium.

Further reading here

Also discussed in this question Why does nitration of aromatic amines give meta directed nitro compounds?

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