Electron spin resonance study of the stereochemistry of radicals related to cinnamic acid

Abstract

The e.s.r. spectra of radicals formed by the oxidation of hydroxycinnamic acid derivatives are reported and ambiguities in the assignments of coupling constants are resolved by means of graphical methods and also by using a tested theory. The time-averaged dihedral angle between the double bond and the ring seems to be of the order of 30°, and this is increased to ca. 60° by a methyl substituent on the β-carbon atom.