The original problem

My attempt

I am mostly concerned about the first step. Are there any species in this mechanism that look too reactive for this mechanism to make sense? Any thoughts would be greatly appreciated.


The accepted mechanism is here: 1

KOH attacks the carbonyl of the urea, the tetrahedral intermediate breaks down with Me-N=N-O- leaving. This picks up a proton from solvent to give Me-N=N-OH. The second step is OH- removing a proton from the Me group of Me-N=N-OH which then loses OH- giving diazomethane.

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  • 1
    $\begingroup$ The mechanism cited by @Waylander involves attack of base at the carbonyl group is an "accepted" mechanism but your approach is not unreasonable with some adjustment to arrow pushing. Your initial step provides no role for base implying that N-nitrosomethylurea is unstable or unstable in water. Instead, deprotonate the amide nitrogen with base is required in your mechanism. The decomposition of isocyanic acid is fine. For the species CH3N=N-OH, use the electron pair on the lefthand nitrogen to eliminate OH-, then deprotonate CH3NN+ with base to get CH2N2. $\endgroup$ – user55119 Jun 14 '18 at 21:34

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