Use of Nitroso Compounds as Scavengers for the Study of Short-Lived Free Radicals in Organic Reactions.

Nitrogen-centered radicals produced by the action of Ag(0) or Ag(1)-amine systems on N-chloroazacyclononane, N-chloropiperidine, and N-chlorosuccinimide have been trapped using 2-methyl-2-nitrosopropane. The resulting nitroxides exhibited e.p.r. spectra consistent with structures 1, 2, and 3. Hydrogen gas evolved during reaction of the chioranlines with Ag(0) was shown to arise completely from the arnine derivatives.Excess Ag(0) reduced the succinamidyl radical to give the silver salt of succinimide.Les radicaux centres sur I'azote et obtenus par action des systemes Ag(0) ou Ag(1)-amine sur le N-chloroazacyclononane, I?-chloropiperidine, et N-chlorosuccinirnide ont Cte piegCs en utilisant du methyl-2 nitroso-2 propane. Les nitroxydes qui en resultent, montrent des spectres r.p.e. compatibles avec les structures 8 , 2, et 3. Le digagen~ent gazeux obtenu dans la reactior, des chloramines sur Ag (0) In connection with our studies of chloramine decomposition by silver ions or metallic silver (1) it seemed desirable to have independent evidence for the post~rlated nitrogen-centered radicals. The produces from reaction of hypochlorites (2), hypobromites, and aliphatic chloramines (1) with finely divided silver were consistent with reduction to give the oxygen and nitrogen-centered radicals respectively. However the reaction of aliphatic chloramines with silver salts was more controversial. While considerable evidence has been provided by Gassman for heterolytic fission of the W-C1 bonds in a number of cases (3), our studies showed that this did not take place at room temperat~are with N-chloropiperidine or medium ring chloramines. The need for amine to initiate reaction, the formation of parent secondary anline: and the sensitivity of the reactions to oxygen led us to conclude that traces of metallic silver were initiating these reactions a!so. This conclusion is now supported by radical trapping evidence.N o radicals were detected when a degassed soliltion of N-chlorsaaacyclononane, indolizidine, and silver perchlorate in 90% aqueous acetonitrile was examined In the e.p.r. speclrorneter. However if 2-methy"l-i-nitrosopropa11e (4) was present during the reaction, a nitroxide with hyperfine splitting consisteent with striictcre 1 was observed. Tile same i~itroxicle was formed when the chlorarnine was treated in cactio with --lNRGG No. 12946. metallic silver in the presence of the nitroso compound. In a similar manner the radical 2 was identified in reaction of N-chloropiperidine with silver.We conclude that silver induces homolytic fission of the chloramines as in eq. 1. A comparable reaction of N-chlorosuccinimide and N-bromosuccinimide takes place and the succinirnidyl radical was trapped in the N-chloro case as nitroxide 3. However preparative runs ill RzNCl + Ag(0) + R z N f AgCl with N-bromosuccinimide showed that the succinarnidyl radical was rapidly reduced further to the anion (eq. 2). This provides a convenient high yield route to the silver salt of succinimide. The stability of the aslion must contribute mar...

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“…time scale. The rather large a, of 18.8 G may arise from such steric effects, as well as from solvent polarity (7).…”

Section: Electron Paramagnetic Resonance Resultsmentioning

confidence: 99%

“…The second radical found in both the above systems with a coupling constant of 16 @ is probably di-t-butyl-nitroxide (7).…”

Section: Electron Paramagnetic Resonance Resultsmentioning

confidence: 99%

Radical Intermediates In Chloramine and N-Chloroimide Reactions

Edwards¹,

Paskovich²,

Reddoch³

1973

Can. J. Chem.

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“…However, in those cases where the metal ion has no nuclear spin, it is not easy to make a clear distinction between free nitrosodurene anion radicals and coordinated ones. Probably, the triplets observed by Giannotti et al (11) and Gasanov and Freidlina (12), originally assigned to U(IV) or U(III) and Cr(CO) 5 Cl spin adducts, respectively, correspond to the nitrosodurene anion radical.…”

Section: Thementioning

confidence: 99%

“…It could be detected during many different photoreactions, e.g. [Cr(CN) 5 NO] 3 " in alkaline methanol, NCV and NO 2 in alcohols, and UO 2 2+ in CH 2 C1 2 / alcohol (9). Surprisingly, ND~' was also observed during the photolysis of Ce(IV) in alcohols (10).…”

Section: Introductionmentioning

confidence: 99%

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Spin trapping in photochemistry of coordination compounds

Rehorek¹,

Hennig²

1982

Can. J. Chem.

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DETLEF REHOREK and HORST HENNIG. Can. J. Chem. 60, 1565Chem. 60, (1982.The application of spin-trapping technique to detect short-lived paramagnetic species formed during photochemical reactions of coordination compounds is reviewed. Interference of radical recombinations by scavenging action of spin traps has been pointed out to be important at high spin-trap concentrations only. Due to only a limited extent of side reactions, nitrosodurene and phenyl N-/

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Application of Electron Spin Resonance Spectroscopy to Photochemistry

Wan

1974

Advances in Photochemistry

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Use of Nitroso Compounds as Scavengers for the Study of Short-Lived Free Radicals in Organic Reactions.

Cited by 83 publications

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Radical Intermediates In Chloramine and N-Chloroimide Reactions

Radical Intermediates In Chloramine and N-Chloroimide Reactions

Spin trapping in photochemistry of coordination compounds

Application of Electron Spin Resonance Spectroscopy to Photochemistry

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