MOLECULAR COMPARISONS OF SELECTED HERBICIDES AND THEIR SAFENERS BY COMPUTER-AIDED MOLECULAR MODELING

The chemical structures of selected herbicides and their respective safeners were modeled by means of the computer-aided molecular modeling program xicamm and compared to determine the molecular similarities of these agrochemicals. The particular safener/herbicide combinations that were evaluated included dichlormid/EPTC, fenclorim/pretilachlor, flurazole/alachlor, oxime ether safeners (cyometrinil, oxabetrinil, and CGA-133205)/metolachlor, naphthalic anhydride/EPTC or metolachlor, and CGA-154281/metolachlor. Comparisons were based on calculated parameters including connectivity indices, charge distribution, and molecular volume as well as visual evaluations of the modeled structures. The results obtained from these comparisons indicate that the chemical components of the most successful safener/herbicide combinations are quite similar at the molecular level. Evaluations of the oxime ether analogues cyometrinil, oxabetrinil, and CGA-133205 which protect grain sorghum [Sorghum bicolor (L.) Moench] against the chloroacetamide herbicide, metalachlor, revealed that as the effectiveness of the safener increases, so does its molecular similarity to metolachlor. Calculated parameters and visual evaluations of the modeled structures showed that CGA-132205, the most effective of the oxime ether safeners is also the most similar to the herbicide at the molecular level. © 1990, American Chemical Society. All rights reserved.