The study reinterpreted the electron spin resonance spectrum of semiquinone intermediates during the photolysis of tetrachloro-p-benzoquinone in ethanol. The spectrum was found to be due to the semiquinone anion formed by one-electron transfer from the solvent ethanol, rather than the semiquinone radical. The reaction was more efficient for chloranil and fluoranil compared to p-benzoquinone and dichloro-p-benzoquiones.