Reactions of pyrazine radical anions in solution. II. Oxidation reduction equilibrium between radical anions of pyrazine and anthracene

Abstract

The relative electron affinity of pyrazine (pz) and anthracene (A) has been determined in 1,2-dimethoxyethane (dme) solution. Electron spin resonance and spectrophotometric methods were employed to study the equilibrium: (pz^-,K⁺) + A ←→ pz + (A^-,K⁺) The equilibrium constant for this reaction has been calculated, after consideration of other reactions of the pyrazine radical anions in the solution, and modified for the case of the equilibrium reaction of the unassociated radical anions. The resultant value has been used to calculate the relative solution electron affinity of pyrazine, which was determined to be of the order of 0.09 eV smaller than that of anthracene in dme. The free energies of solvation of the radical anions of pyrazine and anthracene have been estimated and a value of the gaseous electron affinity of pyrazine calculated.