Ion-radical mechanism of polymer-nitrogen dioxide interaction

Exploring the Chemistry of Electron-Accepting Molecules in the Cavities of the Basic Microporous P4VP Polymer by in situ FTIR Spectroscopy

“…When polymers are considered, a further decomposition of cation-radicals can occur, with the consequent release of protons and the formation of macro-radicals, which undergo recombination with NO and are transformed into the corresponding nitroso compounds. These stable nitrogen-containing radicals are known to be efficient spin traps …”

“…These stable nitrogencontaining radicals are known to be efficient spin traps. 50 The sequence of spectra reported in Figure 7 demonstrates that when NO 2 /N 2 O 4 reacts with P4VP, a proton is formed, together with NO 3groups. Following the mechanism suggested above for the liquid-phase nitration of aromatic compounds, 51 we hypothesize that the first step of the reaction leading to proton abstraction is the formation of an intermediate cationic-radical species, followed by the abstraction of a proton from the most reactive carbon atom of the P4VP chain (the tertiary carbon atom), as seen in part a of Scheme 2.…”

Polymers in polluted atmosphere. Free radical and ion-radical conversions initiated by nitrogen oxides

“…Ab initio calculations [33] show that these dimers are formed with the most probability in NO 2 atmosphere; the form of nitrosyl peroxynitrite ONOONO is too unstable to be considered as an efficient participant of reactions, however it can play the role of an intermediate compound at oxidation of nitric oxide by oxygen [36]. As NN has strong oxidative properties [37], the generation of radicals can take place by an electron transfer from donor functional groups with the formation of intermediate radical cations [9,38]:…”

“…Fig. 10 represents the IR spectra of the original PVPyr films and the same films exposed to NO 2 (5×10 -4 mol×l -1 ) [38]. After 90 min exposure at room temperature, two intense bands were observed in the spectrum at 24002600 and 2200 cm -1 corresponding to the stretching vibrations of NH + pyridinium cations [44].…”

“…During exposure to NO 2 , a band at 1650 cm -1 corresponding to the stretching vibrations of C=N + bonds arises in the spectrum simultaneously with the bands at 24002600 and 2200 cm -1 . This process may be schematically depicted as follows [38]:…”