Diazomethane

A diazo compund is any class of organic substances that have the characteristic atomic grouping: R2C=N+=N- as a part of their molecular structure. R represents a hydrogen atom or any of a large number of organic groups. The most common diazo compound is diazomethane which is a toxic, explosive yellow gas usually prepared as a solution in ether and often used in laboratory procedures for converting carboxylic acids into their methyl esters or into their homologues.

Note: the "2" represents R2, and is supposed to appear as a small "2"

     The "+" and "-" appear on the top of each "N"