FREE-ENERGIES OF ELECTRON-TRANSFER FROM KETYLS TO ISOTOPICALLY SUBSTITUTED KETONES

A series of electron transfer competition reactions between several is otopically different benzophenones was established in liquid ammonia. The resulting electron transfer (A.- + B = A + B.-) equilibrium consta nts were determined via EPR studies and via the physical separation of the anion radical phase from the neutral molecule phase. This anion r adical-neutral molecule separation leads to a partial separation of th e isotopic isomers involved due to the deviation of the equilibrium co nstants from unity. Mass spectral analysis of the two phases yields th ermodynamic data for the electron transfer that is consistent with the EPR results: when A = benzophenone, K(eq) at -75-degrees-C equals 0.5 2, 0.50, and 0.83 for equilibria involving B = perdeuteriated benzophe none, [carbonyl-C-13]benzophenone, and [sym-dodeca-C-13]benzophenone, respectively.