hexane‐2,5‐dione and (NH4)2CO3

Which of the following statement is INCORRECT?

(A) The product X has a five membered ring.
(B) The product X is aromatic.
(C) The degree of unsaturation of the product X is 3.
(D) The product X has a six membered ring.

Ammonium carbonate will probably lose a proton and one of the carbonyls may be protonated. But from here onwards I can't find any leads. Does the lone pair of other oxygen atom plays a role?

Usually the heat provided may lead to a cyclic structure, but I am not sure.

  • $\begingroup$ Yes it is a cyclic compound. First think, what would happen to ammonium nitrate when it is heated? $\endgroup$ Commented Nov 24, 2019 at 5:57
  • $\begingroup$ Ammonia gas , carbon dioxide and water is released...nitrogen lone pair will attack on carbonyl carbon and the oxygen will attack the other carbonyl carbon...is this assumption correct? But what happens next? $\endgroup$ Commented Nov 24, 2019 at 6:32

1 Answer 1


Heating $\ce{(NH4)2CO3}$ will generate $\ce{NH3 + CO2 + H2O}.$ Out of these, $\ce{NH3}$ will act as a nucleophile as it's the most nucleophilic of the products. Addition of $\ce{NH3}$ to the two ketones, followed by elimination of water molecules (due to the high temperature provided by ∆) will generate the final product as follows:

enter image description here

The product is a five-membered aromatic ring called 2,5-dimethylpyrrole.

  • 4
    $\begingroup$ Try to avoid "lassos" in mechanisms. Use arrows. ;) $\endgroup$
    – user55119
    Commented Dec 2, 2019 at 0:33
  • $\begingroup$ @user55119 Well,my handmade mechanisms tend to have a lot of lassos,still will keep that in mind later :) $\endgroup$ Commented Dec 2, 2019 at 0:45

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