According to an internal test series in FIITJEE, it was given that the following compound decarboxylates on heating,

cyclohexane-1,2-dicarboxylic acid

I know that β-keto acids undergo decarboxylation on heating, but I was not sure about the above compound. So, on searching the internet, I found this post, Why are beta-ketoacids better at decarboxylation than gamma or delta? which seems helpful.

As, it says that for γ-keto acids or δ-keto acids, decarboxylation will most likely not happen with a beautiful explanation. So, I drew a possible mechanism and here's what I came up with:

enter image description here

With the help of the reasoning given by @TOLA3HPPA, I can say that decarboxylation will not happen as opposite charges are much separated, but I'm not sure about the mechanism.

Further, while searching on NIST Chemistry Webbook, I've seen an article named,

The Oxidative Bisdecarboxylation of α,β-Dicarboxylic Acids, J. Am. Chem. Soc., 1952, 74, 4370..

which possibly indicates that the above compound undergoes decarboxylation. So, if α,β-dicarboxylic acid undergoes decarboxylation, then what can be the possible mechanism?

  • $\begingroup$ Possible but improbable mechanism. If your final structure is electroneutral (: = negative charge), how do you bond 2 hydrogens to the same carbon? In my experience decarboxylation doesn't occur although anhydride formation may. $\endgroup$
    – user55119
    Aug 5 '19 at 20:17
  • $\begingroup$ I agree that this is improbable as explained in related post. And, the 2 hydrogens were added automatically by ChemDoodle, the software I used : j $\endgroup$ Aug 6 '19 at 17:39
  • $\begingroup$ So much for ChemDoodle! $\endgroup$
    – user55119
    Aug 6 '19 at 20:09
  • $\begingroup$ Don't forget to manually add any charges to atoms so the implicit hydrogen count can be calculated correctly, such as in this case. Would be cool if ChemDoodle could automatically determine implicit hydrogens based on electron pairs if charges aren't provided though. $\endgroup$
    – iclkevin
    Aug 23 '19 at 20:46
  • $\begingroup$ IMO this would form an anhydride on heating, and woudn't decarboxylate. $\endgroup$ Sep 8 '20 at 15:50

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