An electron spin resonance investigation of the radical anions of the benzoylpyridines

Abstract

The radical anions of the three benzoylpyridines have been prepared by electrochemical reduction in dimethyl-formamide. The interpretation of their e.s.r. spectra reveals that the phenyl ring rotates freely in each radical anion. However the rotation of the pyridine ring is restricted in the radical anion of 4-benzoylpyridine. It is possible that the rotation of the pyridine ring is also restricted in the radical anion of 2-benzoylpyridine but in the radical anion of 3-benzoylpyridine the pyridine ring appears to be rotating at an intermediate rate. Molecular orbital calculations have been employed as an aid to the assignment of the splitting constants in each of the radical anions.