Say I have acetohydrazide ($\ce{CH3CONHNH2}$).

Is it possible, that when I add an acid, an intramolecular condensation reaction occurs, forming the cyclic compound 3-methyl-1⁠H-diazirine:


Furthermore, in general, the mechanism of such a reaction is nucleophilic substitution, right?

  • 2
    $\begingroup$ Nope, no chance. Three-atomic rings are extremely strained, even more so with double bonds in the ring, so they form only in reactions with extremely high-energetic particles, such as carbenes. $\endgroup$
    – permeakra
    Feb 18, 2015 at 15:09
  • $\begingroup$ But if we, for a second, discount the strain factor, such a reaction will be possible right? $\endgroup$
    – Lexicon
    Feb 18, 2015 at 15:23
  • 1
    $\begingroup$ Your starting material is a hydrazide. Where is the semicarbazone? $\endgroup$ Feb 18, 2015 at 15:34
  • $\begingroup$ @DhananjayGupta The usual synthesis of imidazole (see wiki for the structure) involves condensation of o-phenylenediamine with formic acid. But you can't dismiss strain factor here. $\endgroup$
    – permeakra
    Feb 18, 2015 at 16:05
  • $\begingroup$ To avoid the strain, it would be much more likely for an intermolecular condensation to occur. $\endgroup$
    – jerepierre
    Feb 18, 2015 at 17:51

1 Answer 1


Your reaction product is a double bond isomer of a diazirine.

Halogene-substituted derivatives of the latter are typically prepared via oxidation of amidines with hypochlorites (Graham oxidation).

Heating your hydrazide in an aqueous solution of a mineral acid will only turn it to the corresponding carboxylic acid.


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