Further nitroxide-producing reactions of aromatic C-nitroso-compounds in benzene solution

Abstract

E.s.r. studies show that nitrosobenzene and 2,4,6-trichloronitrosobenzene react slowly in benzene solution under nitrogen with many carbonyl compounds to give moderately stable nitroxides formed by additions to their enolic tautomers. The formation of nitroxides from diethyl and di-isopropyl ketones may involve a further molecular rearrangement. Short lived arylnitroxides ArNHO· are probably formed also and sometimes can be detected as transient initial products of reactions between nitroso-compounds and arylhydroxylamines, hydrazobenzene, thiols, and a few phenols. Thiophenols react with these nitroso-compounds to give thionitroxide radicals ArN(O·)SAr′, but alkylated phenols yield first the corresponding aryloxyl radicals and then either benzylic or nuclear-substituted nitroxides, depending on the structures of their substituent groups.

The hyperfine splitting constants of the new nitroxide radicals observed in this study are tabulated. The work illustrates the general tendency of aromatic C-nitroso-compounds to exhibit free radical reactivity in a non-ionizing solvent.