Intermediates Involved in the Oxidation of Nitrogen Monoxide: Photochemistry of the cis‐N₂O₂⋅O₂ complex and of sym‐N₂O₄ in Solid Ne Matrices

Abstract

Pure sym-N(2)O(4) isolated in solid Ne was obtained by passing cold neon gas over solid N(2)O(4) at -115 degrees C and quenching the resulting gaseous mixture at 6.3 K. Filtered UV irradiation (260-400 nm) converts sym-N(2)O(4) into trans-ONONO(2), a weakly interacting (NO(2))(2) radical pair, and traces of the cis-N(2)O(2)O(2) complex. Besides the weakly bound ONO(2) complex, cis-N(2)O(2)O(2) was also obtained by co-deposition of NO and O(2) in solid Ne at 6.3 K, and both complexes were characterised by their matrix IR spectra. Concomitantly formed cis-N(2)O(2) dissociated on exposure to filtered IR irradiation (400-8000 cm(-1)), and the cis-N(2)O(2)O(2) complex rearranged to sym-N(2)O(4) and trans-ONONO(2). Experiments using (18)O(2) in place of (16)O(2) revealed a non-concerted conversion of cis-N(2)O(2)O(2) into these species, and gave access to four selectively di-(18)O-substituted trans-ONONO(2) isotopomers. No isotopic scrambling occurred. The IR spectra of sym-N(2)O(4) and of trans-ONONO(2) in solid Ne were recorded. IR fundamentals of trans-ONONO(2) were assigned based on experimental (16/18)O isotopic shifts and guided by DFT calculations. Previously reported contradictory measurements on cis- and trans-ONONO(2) are discussed. Dinitroso peroxide, ONOONO, a proposed intermediate in the IR photoinduced rearrangement of cis-N(2)O(2)O(2) to the various N(2)O(4) species, was not detected. Its absence in the photolysis products indicates a low barrier (<or=10 kJ mol(-1)) for its exothermic O-O bond homolysis into a (NO(2))(2) radical pair.

Heterocumulene Sulfinyl Radical OCNSO

“…The IR difference spectrum showing the change of the matrix upon photolysis is given in Figure . Almost 80 % of OCNSO decomposed after 20 minutes of irradiation, no isomers (e.g., O 2 SNC, O 2 SCN, and OSOCN, Table S2 in the Supporting Information) but only the fragmentation species CO, OSN/SNO, OCS, and NO were identified. Therefore, similar to the photo‐induced CO elimination of covalent isocyanates, OCNSO eliminates CO and furnishes OSN, and the latter undergoes photoisomerization into SNO .…”

Kinetic study of the nitric oxide oxidation between 288 and 323 K, under pressure, focus on the oxygen influence on the reaction rate constant

“…More recent studies 29–31 observed the formation of the intermediate NO 3 at atmospheric pressure, at ambient temperature, and at lower temperatures. On the other hand, Beckers et al 32 came to the conclusion that the nitric oxide oxidation mechanism involving the nitric oxide dimer (NO) 2 then the formation of various N 2 O 4 species from the N 2 O 2 . O 2 complex.…”

Silver‐Catalyzed Chemo‐ and Regioselective Nitration of Anilides

“…At first, arylsilver complex C is formed via coordination of silver catalyst to the acetylamino directing group,[33b] which subsequently provides N ‐phenyl acetamide radical D and Ag 0 which is reoxidiszed to Ag I in presence of K 2 S 2 O 8 . Intermediate D reacts with in situ generated NO 2 radical, , to give the ortho ‐nitrated product 2b . To prove the radical mechanism, a control reaction was carried out using 2,6‐di‐ tert ‐butyl‐4‐methylphenol (BHT) as a radical scavenger.…”