ESR Spectra of the Anion Radicals of 2,5-Dimethyl−2,4-hexadiene and Glyoxal

Electrolysis of tetrahydrofuran solutions at low temperatures yields a short-lived paramagnetic species at the cathode which has a single ESR absorption line. Electrolysis in tetrahydrofuran reduces 2,5-dimethyl−2,4-hexadiene, whereas this is not observed under similar conditions in liquid ammonia. The radical anion of this molecule in tetrahydrofuran has the following coupling constants (in gauss): aH(6 protons)=9.91±0.05, aH(6 protons)=8.75±0.05, and aH(2 protons)=1.16±0.21. The glyoxal anion shows an intense 1:2:1 triplet with a splitting constant of 7.63±0.01 G in tetrahydrofuran. Effects of substitution and solvation on spectra of radicals with this isoelectronic pi-orbital structure are discussed.