High mobility solvent holes in methylcyclohexane

Using time-resolved dc photoconductivity, the migration patterns and reacti ons of solvent hole in liquid methylcyclohexane between 230 and 350 K have been studied. It is shown that solvent holes in liquid methylcyclohexane ar e reversibly scavenged by solutes whose liquid-state ionization potentials are 0.2-0.3 eV below that of the solvent. The reversible electron transfer is driven mainly by the reaction heat (60-90%); further decrease in the fre e energy is due to increase, in entropy following the destruction of solven t structure around the hole. Between 133 and 360 K, the solvent hole diffus es with activation energy of 7.8 kJ/mol; the fastest electron-transfer reac tions (ca. 8.7 x, 10(10) M-1 s(-1) at 25 degreesC) have activation energies between 3.9 and 5.3 kJ/mol (250 to 350 K). Unusually large scavenging radi i, 1.5-3 run, were obtained for these charge-transfer reactions.