The nitrosation of aniline with Zn(py)2(ONO)2

Diazoaminobenzene (DAAB) formed slowly when aniline was reacted with Zn(py)₂(ONO)₂ in dichloroethane at 60°. The rate of reaction was followed by measuring the DAAB concentration spectrophotometrically at 353 nm. Complex concentrations ranged from 5 to 30 mM, while those of aniline were from 100 to 900 mM. The kinetic data were explained by a mechanism involving a pre-equilibrium, wherein aniline displaced a nitrite ion from the zinc complex. This was followed by a slow reaction of the free nitrite ion with the solvent, forming a highly reactive nitrosating species.