IS HYDRAZOIC ACID (HN3) AN INTERMEDIATE IN THE DESTRUCTION OF HYDRAZINE BY EXCESS NITROUS-ACID

The kinetics of the decomposition of NH2N=NOH, the intermediate absorb ing at 225 nm formed in the nitrous acid-hydrazine reaction have been studied by stopped-flow spectrophotometry at acidities up to 1 mol dm( -1) H+. A substantial amount of protonation occurs at high acidities, and the pK(a) of NH3+N=NOH is 0.57. In excess hydrazine decomposition occurs to form hydrazoic acid (HN3), but in excess nitrous acid a rapi d second nitrosation occurs by a diffusion-controlled reaction between NO+ and NH2N=NOH which can bypass this pathway, though the possibilit y of some hydrazoic acid formation cannot be ruled out. Spectrophotome tric evidence has been obtained for the formation of a relatively stab le species, probably a very minor component, a product of the double-n itrosation reaction.