Physicochemical-activity relationships in asymmetrical analogues of methoxychlor

Compounds of the general formula 2-aryl-2-(p-methoxyphenyl)-1,1,1-trichloroethane have been prepared and tested for toxicity toward houseflies, pretreated for 1 h with 2mug of piperonyl butoxide. The majority of the compounds synthesized were chosen with the aid of computer programs designed to ensurewell-spread sets of minimally correlated physicochemical parameter values. A nonlinear two-dimensional representation was used to map the active region of physiochemical parameter space and a regression equation was obtained relating the observed toxicity to a combination of these physicochemical parameters. The equation indicates that toxicity increases with the hydrophobicity of the molecules but is decreased markedly by the introduction of bulky substituents into the ortho positions of the benzene ring and less markedly by bulky substituents in the meta and para positions. Substituents which donate electrons to the benzene ring by the "resonance" effect favor high toxicity. The equation performs well in forecasting the toxicity of further members of the series.