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The given answer is (A). At first I thought that it was a simple decarboxylation (due to high heat).

But that does not seem feasible at all as the ring has no electron withdrawing groups which stabilise the carbanion; infact it has electron donating groups which rules out decarboxylation. What else could be a possible mechanism here?

Edit:In the answer posted below could anyone explain how the hydrolysis of triamminobenzene occurs?

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    $\begingroup$ Redraw the starting material as its imino tautomer and maybe it will become clearer $\endgroup$
    – Waylander
    Jun 29, 2020 at 6:37
  • $\begingroup$ It is normal decarboxylation - pericyclic. Carbanion isn't usual intermediate. $\endgroup$
    – Mithoron
    Jun 29, 2020 at 15:15

1 Answer 1

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My initial guess for the product was Phloroglucinol, or 1,3,5-trihydroxybenzene1,2

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Belskaya et al.3 says that 1,3,5-triaminobenzene can be formed, but it can eventually be hydrolyzed to Phloroglucinol

enter image description here enter image description here

The sources mention decarboxylation as the mechanism. Note that it is the trihydroxylamine 10 that is getting decarboxylated here. The mechanism becomes clearer if you consider the imino tautomers 6 or 7 with the acid group attached and then dehydrate.

In short, Phloroglucinol should be the final product. If that is not one of the options, then 1,3,5-triaminobenzene is the answer you should select.

References:

  1. “PHLOROGLUCINOL.” Organic Syntheses, vol. 9, 1929, p. 74. doi:10.15227/orgsyn.009.0074
  2. Tewari, K.S and Vishnoi, N.K : A textbook of organic chemistry, 4th edition.
  3. Olga B.Belskaya, Valentin P.Talsi, Roman M.Mironenko, Vladimir A.Rodionov, Sergey V.Sysolyatin, Vladimir A.Likholobov, "Transformation pathways of 2,4,6-trinitrobenzoic acid in the aqueous-phase hydrogenation over Pd/C catalyst", Journal of Molecular Catalysis. doi: 10.1016/j.molcata.2016.04.014
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  • $\begingroup$ Did you notice it's "side reactions" there? It's not usual at all. Also catalytic hydrogenation environment can influence things. $\endgroup$
    – Mithoron
    Jun 29, 2020 at 15:19

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