Nitration of pyrene adsorbed on silica particles by nitrogen dioxide under simulated atmospheric conditions

Nitration of adsorbed pyrene on silica particles with nitrogen dioxide was studied under condition of room light in a simulated atmosphere. An induction period was present in the nitration process. Nitric acid formed on the silica particles acted as the catalyst, and the reaction proceeded autocatalytically. Electron donating substituents promoted the reaction, while the electron-attracting substituents diminished it. An electrophilic nitration mechanism involving HNO2+ and HN2O4 as electrophiles was proposed for the reaction