AbstractThe larvicidal activity of a number of 1‐(substituted benzoyl)‐2‐benzoyl–1‐ten‐butylhydrazines against the rice stem borer (Chilo suppressalisWalk.) was measured. Variations in the activity were examined quantitatively using physico‐chemical substituent and molecular parameters and regression analysis. The results indicated that the molecular hydrophobicity and the electron‐withdrawing inductive/ field effectof onthosubstituents are favourable to larvicidal activity. The bulkiness of substituents at themetaandparapositions was unfavourable to activity, substitution at theparaposition being more unfavourable than that at themetaposition in terms of van der Waals' volume. The 2,3–, 2,5‐ and 2,6‐disubstitution patterns were also unfavourable to activity. Reductions in larvicidal activity caused by the 2,6‐,‐ 2,3,5‐ and 2,3,4,5‐substitutions were greater than those induced by the 2,3‐ and 2,5‐disubstitutions. When the sum of contributions from favourable effects is greater than that from unfavourable effects, the larvicidal activity is expected to be superior to t
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