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I really want to know how this reaction works: \begin{align} \ce{SC(NH2)2 + 2 NH3 &-> CH2N2 + 2 NH4+ + S^2-}\\ (\ce{S=C(NH2)2 + 2 NH3 &-> H2C=N=N + S(NH4)2 }) \end{align}

This seems like it ought to be a pretty simple mechanism, but I don't know a lot about organosulfur chemistry and I am having difficulty explaining this reaction to myself. This reaction will also occur with thioacetamide, forming N-mathanimine ($\ce{CH3-N=CH2}$) if that helps. Also, thiourea does thione-thiol tautomerism.

MY friend and I scribbled some arrows. I don't think it's a good mechanism, but is this the general idea?

proposed mechanism

Does this make any sense?

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  • $\begingroup$ Have you a reference or source for the reaction? $\endgroup$
    – Beerhunter
    Apr 13, 2016 at 21:12
  • $\begingroup$ I am doing the chemical bath cadmium sulfide precipitation, so my real mechanism may involve coordination around cadmium (II), but the J. Chem. Educ. paper says "it is well-known that (NH2)2CS yields S2-ions in basic media", so I assume the reaction between thiourea and ammonia works even without the cadmium (Ibanez, J. G. et al., J. Chem. Educ. 68(10), 872.). This paper has it reacting with hydroxide to form water (rather than ammonia to ammonium), but it shows that CH2N2 is indeed the byproduct: ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1022931 $\endgroup$
    – gannex
    Apr 13, 2016 at 22:29

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