Spin Trapping of Free Radicals Generated from Arylazo <i>p</i>-Tolyl Sulfones

Abstract

Abstract Arylazo p-tolyl sulfones(I) were thermolyzed or photolyzed in the presence of trapping agents such as α,N-diphenyl nitrone(II), α-phenyl N-t-butyl nitrone(III) and 2-methyl-2-nitrosopropane(X). ESR studies showed that phenyl radical or p-methoxy phenyl radical is produced from the decomposition of I and adds to II or III. The adduct of phenyl radical to II and that of p-methoxyphenyl radiacl to III were synthesized for comparison by separate pathways. The photolysis of phenyl p-tolylazo sulfone(Ia) in the presence of III yielded benzhydryl t-butyl nitroxide, benzoyl t-butyl nitroxide and t-butyl p-toluenesulfonyl nitroxide(XVI) radicals. The photolysis of la in the presence of X gave di-t-butyl nitroxide(XII) and XVI. The photolysis of phenylazotriphenylmethane in the presence of X yielded XII and t-butyl nitroxide radical. The mechanisms of the formation of these radicals are discussed. The formation of arenesulfonyl radicals from the decomposition of I has been proved indirectly (analyses of the products of the combination of nitroxide radicals with arenesulfonyl radicals) and directly (detection of t-butyl p-toluenesulfonyl nitroxide radical.