Generation of aminyl and aminium radicals by photolysis of N-nitrodialkylamines in solution

Abstract

Photolysis of nitramines in a neutral solvent generated nitrogen dioxide and aminyl radicals which abstracted a hydrogen but did not add to a π-bond. In dilute acidic solution, the aminyl radicals generated from the photolysis were protonated to the corresponding aminium radicals that preferentially added to π-bonds rather than abstracted a hydrogen. However, complex mixtures of addition products were obtained when nitramines were photolysed in the presence of cyclohexene under nitrogen. The plethora of the products is believed to arise from the complex behavior of nitrogen dioxide in solution; for example, (i) nitrogen dioxide may react as O- or N-radical, (ii) nitrogen dioxide exists in equilibrium with nitrogen tetraoxide, and (iii) both oxides can react as oxidizing or radical trapping agents. Under oxygen, the oxidative addition of nitramines to cyclohexene gave 1-dialkylamino-2-nitratocyclohexenes which could be treated with lithium aluminium hydride to give good yields of the corresponding amino alcohols. The quantum yields of nitramine disappearance indicated that the photolysis followed short chain processes either in neutral or acidic conditions. The decrease in quantum yield at >2 N H2SO4 is believed to be due to a reduced reactivity of aminium radicals in a highly acidic environment. The probable mechanisms of these photolytic radical chain processes are discussed.

Photochemistry of Imidacloprid in Model Systems

“…As in the present study, photoaddition products of N -nitrodialkylnitramines and cyclohexene were not obtained. The photolysis is explained by Chow et al by a radical mechanism where in an initial step homolytic cleavage of the N−N bond generates nitrogen dioxide and the aminyl radical, which could undergo further reactions. N−N bond cleavage can also be assumed during the photolysis of 1 resulting in 5 by hydrogen transfer from the organic solvents ( Scheme ).…”

“…A possible intermediate in the formation of 2 is N -nitrosoimidacloprid ( 6 ). Nitrosamines are described as main photoproducts of nitramines , and during irradiation of 1 on leaves of tomato plants, Scholz and Reinhard observed 6 as one of four main photoproducts. But, during the irradiations of 1 in our solvent systems, 6 could not be identified as photoproduct.…”

“…A possible reaction mechanism was delivered by Chow et al (25) who carried out photolysis studies with N-nitrodialkylnitramines in different solvents such as methanol, n-hexane, and acetonitrile in the presence and absence of cyclohexene. These irradiation experiments resulted in the corresponding amino, formamido, or nitroso compounds in different ratios depending on the solvent and the reaction conditions.…”

Molecular Rearrangement. 36. Selective α-CH Oxidation of Alkylarenes by Nitrogen Dioxide on Thermolysis with Nitramines

“…Formation of formaldehyde and N -methyl- N -nitrosoaniline from thermolysis of the N -nitroaniline 1 with N , N -dimethylaniline can be rationalized as depicted in Scheme 8.

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Addition reactions of aminium radicals: oxidative and non-oxidative photoaddition of nitrosoamines to non-conjugated polyenes

“…After irradiation (2.5 h), the photolysate was concentrated to 30 ml and water (50 ml) was added. The mixture was then extracted with ether (3 x 40 ml). The ether extract was washed with water (2 x 30 ml), dried, and evaporated to give an oil (440 mg) which showed no n.m.r.…”