Photolysis of some N-nitroso- and N-nitro-anilines in solution

Abstract

The photolyses of three N-methyl-N-nitrosoanilines and two N-methyl-N-nitroanilines in organic solvents have been studied in the range of 300-340 nm. The influence of solvent character and the presence or absence of oxygen play important roles in the product composition range. The primary photochemical process involves N-N fission, this being homolytic in aprotic solvents and heterolytic in methanol. Three novel mechanistic conclusions are proposed, namely photosolvolysis of a nitrosamine in methanol, photooxidation of nitrosamines in aprotic solvents and the production of biphenyl derivatives on photolysis of nitro-substituted nitrosamines and nitramines in aromatic solvents.The reaction of nitrogen dioxide with N-methyl-4-nitroaniline produces a variety of products. In the course of a study of these reaction products it became apparent that some of the Nnitroso and N-nitro compounds produced displayed interesting photochemical reactions. Our earlier studies on the photochemistry of many C-nitroso compounds 1 and a couple of Nnitroso compounds 2 had demonstrated the importance of solvent character in photolyses where nitric oxide was a primary photochemical product. It was therefore of interest to study the photolyses of aromatic N-nitroso compounds paying attention to any differences between protic and aprotic solvents. The compounds chosen in this investigation comprise three nitrosamines and two nitramines.

Mechanism of Photochemical O-Atom Exchange in Nitrosamines with Molecular Oxygen

“…In contrast, a stepwise route from 7 + 3 O 2 to B was found by a large barrier via consecutive transition states, TS7/B and TS7/ B′. Although dioxaziridine N-oxide (8) is similar to dioxaziridines and peroxy acid dioxiranes (9) 52 that can exchange an 18 O peroxy acid oxygen (Scheme 5), we do not find evidence for 8 on the potential energy surface after a detailed search of conformational space. We note the addition of 1 O 2 to 7 is also computed, but it is tempting to suggest charge-transfer 1 O 2 physical quenching to 3 O 2 , a channel that is significant in azides, amines, and hydrazines, 53−56 where tertiary …”

“…27 Furthermore, the photocyclization of A and B is similar to that reported for the photocyclization of nitrosooxide to dioxaziridine, 35,42,65 where 18 O labeling also showed aryl dioxaziridines arise in the photooxidation of aryl azides (λ > 350 nm) using 18 O 2 gas by photocyclization of the aryl nitrosooxide. 40,41 In summary as described above, a photochemical process that transposes an 18 O label from molecular oxygen 18 O 2 was seen for nitrosamines 1 and 2, but not for 3 and 4. The 18 O-atom source was found not to be from moisture based on control photolysis experiments with 18 …”

“…40,41 In summary as described above, a photochemical process that transposes an 18 O label from molecular oxygen 18 O 2 was seen for nitrosamines 1 and 2, but not for 3 and 4. The 18 O-atom source was found not to be from moisture based on control photolysis experiments with 18 …”

“…Scheme 4 shows that 18 ( 1 O 2 ) was generated from a chemical source [ 18 O− 18 O labeled naphthalene endoperoxide of N,N′-di(2also failed to exchange an 18 O atom into 1. The thermal decomposition of DHPN 18 O 2 was carried out in the presence of 1 in CH 3 CN/D 2 O buffer phosphate (2:1) at pD 7.4 and also in a two-phase CHCl 3 /D 2 O buffer phosphate (2:1) system at pD 7.4 with stirring for 1 h at 37°C.Figure S6(Supporting Information) shows the HPLC-MS/MS of18 O-labeled endoperoxide of DHPN 18 O 2 before and after its thermal decomposition. Theoretical evidence that supports the reaction in Scheme 3 is described next.Computed Energetics.…”

Charge-density analysis of 1-nitroindoline: refinement quality using freeRfactors and restraints

“…Simple and small organic molecules of the nitramine class seem to be interesting models for investigations in the field of charge-distribution analysis. An interesting feature of the aromatic N-nitro compounds is their ability to rearrange under the influence of an acid, elevated temperature or on photolysis (Growenlock et al, 1997). The migration is entirely intramolecular, i.e.…”