ELECTRON-ATTACHMENT TO BENZENE AND TOLUENE IN NONPOLAR-SOLVENTS AT HIGH-PRESSURE

The effect of dilute concentrations of the aromatic hydrocarbons benzene and toluene on the electron mobility in some nonpolar liquids was studied as a function of pressure from 1 bar to 3 kbar and as a function of temperature from 20 to 100°C. These aromatics have no effect on the electron mobility in n-pentane at low pressure and no effect on the mobility in tetramethylsilane at any pressure or temperature studied. However, above 1 kbar the mobility in n-pentane is reduced by the presence of these aromatics, an effect which increases with pressure. This effect is attributed to reversible electron attachment: es- + aromatic ←+ aromatic-. This equilibrium is shifted to favor the anions at high pressure both because the electron in the solvent becomes destabilized and because the volume change is large and negative, of the order of -100 cm3/mol. The results indicate that the benzene anion is more stable than the toluene anion in solution. © 1990 American Chemical Society.