Estimation of the hydrophobicity of 2,4-diphenyl-1,3-oxazoline analogs and QSAR analysis of their ovicidal activity against Tetranycus urticae

Partition coefficients of six 2-phenyl-1,3-oxazoline congeners containing 2-I, 2-NO2, 2-CF3, 2,6-(CH3)2, 2,6-F2, and 2-F-6-Cl substitutions on the phenyl moiety were measured in a 1-octanol/water system using the flask-shaking method. The effect on the hydrophobicity (Log P) of substituents on the phenyl moiety of 2-phenyl-1,3-oxazolines linearly correlated with that of benzamide congeners. log P values of other 2-(substituted phenyl)-1,3-oxazoline analogs were empirically estimated from the corresponding substituted benzamides. The ovicidal activity of 2-(substituted phenyl)-4-phenyl-1,3-oxazoline analogs against the two-spotted spider mite Tetranycus urticae was quantitatively analyzed using the classical QSAR (Hansch–Fujita) method. Results showed that ovicidal activity increases with hydrophobicity. The introduction of inductive electron-withdrawing groups at ortho-positions increased ovicidal activity, but addition of steric bulk was unfavorable. Substitution at either the meta- or para-position was detrimental to the acaricidal activity.