Electron Transfer Enthalpy Research Articles

Isotopic enrichments via altered first and second solution electron affinities

Electron spin resonance experiments have been utilized to show that the solution electron affinity of benzene-/sup 13/C/sub 6/ is less than that of benzene by 0.24 kcal/mol and that the solution EA of benzene-d/sub 6/ is less than that of benzene by 0.44 kcal/mol. Perdeuteration of naphthalene, anthracene, or perylene results in a very similar lowering of the solution EA of the hydrocarbon as evidenced by the fact that the equilibrium constant for the electron transfer between the hydrocarbon anion radical, X/sup .-/, and the perdeuterated hydrocarbon, Xd (X/sup .-/ + Xd = Xd/sup .-/ + X), is less than unity. Likewise the second EAs of perdeuterated perylene and anthracene are lower than those of the unsubstituted hydrocarbons (K/sub eq/ for X/sup 2 -/ + Xd/sup .-/ = X/sup .-/ + Xd/sup 2 -/ is less than unity). The free energy and enthalpy of electron transfer from the anthracene anion radical to perdeuterated anthracene is 0.41 kcal/mol and that from the anthracene dianion to the perdeuterated anion radical is 0.10 kcal/mol. The fact that these equilibrium constants are not equal to 1 enables one to use the difference in the chemical reactivity of the ions and neutral molecules to selectivelymore » isotopically enrich the hydrocarbons involved.« less