Ionization constants for 10 heterovinylene sets have been correlated with the extended Hammett equation Qx = ασI.x + βσR.X + h. Sets studied include disubstituted oximes, disubstituted glyoximes, syn- and anti-substituted aldoximes, substituted acetyl oximes, substituted methyl oximes, syn- and anti-substituted phenyl oximes, substituted phenylimines, and substituted ethoxyimines. Good results were generally obtained. The magnitude of α is dependent upon molecular geometry. Assignment of configuration by means of correlation with the Hammett equation is discussed. © 1969, American Chemical Society. All rights reserved.