Equilibrium Reactions of Excess Electrons with Aromatics in Non‐polar Solvents

The excess electron in non‐polar solvents is shown to undergo the reversible reaction: e− + A ⇄ A−, with the solutes (A): triphenylene, phenanthrene, naphthalene, styrene and α‐methylstyrene. This was demonstrated by a pulse conductivity method which permitted measurement of both the attachment and detachment rates. The attachment rate constants are very large, near 1013 mol−1 · l · s−1 in (CH3)4Si and 2,2,4‐trimethylpentane solvents and a little less than 1012 mol−1 · l · s−1 in n‐hexane. The detachment rates are very solvent and temperature dependent, characterized by large pre‐exponential factors (1018 ‐ 1023 s−1) which facilitate the very endothermic detachment reactions. The equilibrium data show that these reactions occur with large decreases in enthalpy (‐67 to −109 kJ/mol) and large decreases in entropy (‐84 to −204 J mol K). The equilibrium constants at 298° increase with electron affinity of the solute and also change with solvent. The results show that the ground state energy of the electron changes from liquid to liquid: for tetramethylsilane ΔHsoln) (e−) = −0.64 eV, for 2,2,4‐trimethylpentane ΔHsoln(e−) = −0.40 eV and for n‐hexane ΔHsoln(e−) = −0.18 eV.