Linear free energy relationships of half-wave reduction potentials of (E)-4-aryl-4-oxo-2-butenoic acids

Half-wave reduction potentials of a set of twelve (E)-4-aryl-4-oxo-2-butenoic acids obtained by direct current polarography in methanol are reported. E1/2 is correlated with Hammett sigma values as well as with values of frontier molecular orbitals calculated at a semiempirical molecular orbital level. Constant potential electrolysis of a representative compound shows that the first polarographic wave corresponds to one-electron reduction. The isolation of the product proves reduction of the activated double bond.