Inverted spin trapping. Part IV. Application to the formation of imidyl spin adducts from N-haloimides

Abstract

The photochemically induced formation of imidyl spin adducts from N-haloimides and four spin traps, 2-methyl-2-nitrosopropane (MNP), N-benzylidene-tert-butylamine N-oxide (PBN), 1,1-di-tert-butylethylene (DTBE) and N-methylene-tert-butylamine N-oxide (MBN) has been studied. It is concluded that imidyl spin adducts from MNP, PBN and MBN are most likely formed via the radical cations of the spin traps, formed by reaction between the excited state of the spin trap and the N-haloimide. This type of reaction is a case of inverted spin trapping. For DTBE, this mechanism can only be assigned by analogy, since this molecule cannot be excited by the light source employed. However, it does form imidyl adducts by chemical or photosensitized (using 2,4,6-trianisylpyrylium ion or 9,10-dicyanoanthracene as the sensitizer) oxidation of DTBE solutions containing succinimidate anions, so even in this case inverted spin trapping cannot be excluded.