Summary: Spin-trapping results favor a mechanism in- volving homolytic cleavage of the N-0 bond for the thermal decomposition in benzene of N-pivaloxyacet- anilides, which are models for carcinogenic metabolites of aromatic amides. ... Sir: Sulfuric and carboxylic acid esters of N-hydroxy-N- arylacetamides are important carcinogenic metabolites derived from polycyclic N-arylacetamides including N- acetyl-2-aminofl~orene.~~~ Although dismutation ...