| Abstract: | Quantitative structure-activity relationships in several series of fungitoxic N-(1-substituted-2,2,2-trichloroethyl)formamides and bis1-(2,2,2-trichloroethyl)formamides] were investigated by the Hansch method, employing partitioning data determined by reversed-phase thin-layer chromatography and electronic parameters calculated by the Hückel Molecular Orbital method. The activity of compounds applied as root-drenches against Erysiphe graminis on barley correlated with their partitioning properties alone, but electronic properties of the aromatic derivatives were also influential in leaf-spray tests. Possible factors governing the activity of the compounds are discussed. It is tentatively proposed that the biologically active centre of triforine and related aliphatic compounds includes the XCHNHCO grouping (where X = heteroatom), whereas that of chloraniformethan and its aryl analogues incorporates the grouping RXCHNHCO (where RX = a conjugated system capable of accepting pi-electrons from an electron donating receptor). |
