Collect. Czech. Chem. Commun. 1979, 44, 762-772

ESR study of anion radicals produced in cathodic reduction of 2-furfural derivatives

Andrej Staškoa, Peter Pelikánb, František Tomanovičc and Viliam Pätoprstýa

a Institute of Chemical Physics
b Department of Physical Chemistry
c Department of Analytical Chemistry, Slovak Institute of Technology, 880 37 Bratislava


Furfural and its derivatives are reduced reversibly to the corresponding anion radicals during polarography in dimethylformamide. These radicals have been studied by ESR, and analysis of their spectra has been carried out. The calculated splitting constants and half-wave potentials (INDO method) agree well with the experiment. The maximum spin density of the unpaired electron has been found for the aldehydic proton of the furfural anion (aH = 1.01 mT), the values for the remaining protons of furane ring being smaller (aH3 = 0.115 mT, aH4 = 0.49 mT, and aH5 = 0.64 mT). Introduction of nitro group in 5 position of furfural results in a marked shift of spin density of the nitrogen atom (aN = 0.533 mT) and decrease of density at the aldehydic proton (aH = 0.334 mT). Chenges of half-wave potentials of the individual furfural derivatives correlate well with changes in the respective Hammett constants of the substituents.