Substituent Effects on Aroyloxylation of Aromatic Compounds with Substituted Benzoyloxy Radicals

Abstract

Substituted benzoyl peroxides of the types (P-XC6H'COO)2 and (m-XC6H4COO)2, where X=CsO, H3, H, C1, Br, or NO2, were decomposed in substituted benzenes in the presence of CuC12 at 80 C, and orientation, relative rates and partial rate factors for the aroyloxylation were determined. Plots of the logarithms of the partial rate factors of meta and para position$vs. ti" substituent constants yielded good straight lines, and the electrophilicity of p-XC6H'COO. (p value) was found to be in the following order; P CHsOCsHdCOO. (1.71) P CHsC6H"COO. (1.69) C, H, COOe(1.66) P-CIC, H4COO t(1.61) P-BrC6HdiCOOe(1.59) P-NO, C, H, COO. (1.43). p Value for the aroyloxylation with m-XC6H'COO e ranged from 1.62 with X=Br to 1.74 with X=NO, .
It was also found that in the aroyloxylation of anisole, benzene and chlorobenzene the yield bf the aroyloxylated product was always higher with P-XC6HaCOOe than with C6HsCOO. or m-XC6H4COO.. This finding suggests that the decarboxylation reaction of p-XC6H4COO. is reduced by contribution of resonance effeet!ofipara substituent'ewbX.