Quantitative structure-activity relationships of herbicidal N-alkyl-N-(4-substituted benzyl)-4-chloro-2-pentenamides against Echinochloa oryzicola

The herbicidal activity of N-alkyl-N-(4-substituted benzyl)-4-chloro-2-pentenamides against a barnyard grass species, Echinochloa oryzicola, was evaluated, and the potency variations were quantitatively analyzed using physicochemical parameters for the N-alkyl and the benzyl-benzene ring substituents in the amide moiety. The results indicated that the herbicidal potency was parabolically related with the total hydrophobicity of the amide moiety. The electron-withdrawing property of the benzene-ring substituents as well as their hydrogen-bonding accepting ability was significant in potentiating the herbicidal activity.