Methyldiazonium cation

Step 1 Take a proton away. Proton transfer from the carboxyl group to diazomethane gives a carboxylate anion and methyldiazonium cation. 

Reaction with Diazomethane (Section 17.7B) Diazomethane is used to form methyl esters from carboxylic acids. The mechanism involves protonation of the diazomethane carbon atom by the carboxylic acid to make a methyldiazonium cation, followed by attack of the resulting carboxylate on the methyldiazonium cation to give the methyl ester and Nj. 

The methyldiazonium ion [CH3-N=N]+ is interesting. Later (Section 4.1.5) we will learn that N=N is a very reactive leaving group and indeed it is the best there is, at least of those routinely used in solution chemistry. The computed stmcture of [CH3-N=N]+ shows a weak bond (low value of p) and a high net positive charge (+0.840) on the methyl group. This structural information suggests that [CH3-N=N]+ is a methyl cation weakly bound to N2, and poised to release N,. 

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