Measurement of electrophilic aromatic reactivities via pyrolysis of 1-arylethyl acetates. Part IV. The deactivating effect of the pentafluorophenyl group

Abstract

The rates of pyrolysis of 1-phenylethyl acetate and 1-(pentafluorophenyl)ethyl acetate have been measured between 330·6 and 409·6 °C. At 625 K the latter undergoes elimination 4·60 times slower than the former in contrast to the value of 7·75 predicted from additivity of the effects of the individual fluorine atoms. This confirms the exalted reactivity of pentafluorobenzene obtained in electrophilic aromatic demetallations (carried out in solution) showing this effect to be independent of solvent influences and also not to arise solely from steric acceleration.