title: Role of molecular geometry, valence charge distribution and vibrational modes in bioactivity of cyclodiene insecticides.
abstract: Fourier transform infrared spectral measurement and complete normal mode calculations have been carried out for heptachlor and wedge modes have been identified. In addition, valence charge distributions have been obtained for aldrin, endrin, heptachlor, beta-endosulfan, cis-chlordane, trans-chlordane, photo-cis-chlordane and photo-trans-chlordane using CNDO/2 (complete neglect of differential overlap) molecular orbital calculations. A toxicity parameter has been defined as the product of the charge distribution and surface area of the corresponding active wedges, depending on the interacting structural features. The variation of this toxicity parameter is generally in order and in agreement with the reported measurements based on the corresponding order of observed LD50 values. Because of the structural features, the toxicity in these cases is a surface phenomenon rather than a volume effect as in the case of Gammexane, wherein the insecticide binds itself to membrane channels. Because the biological activity is a dynamic rather than a static phenomenon, it is expected that the normal modes involving the wedge atoms play an important role.
authors.affiliation: Industrial Toxicology Research Centre, Lucknow, India.
authors.forename: P N
authors.initials: PN
authors.lastname: Saxena
authors.forename: V D
authors.initials: VD
authors.lastname: Gupta
mesh_terms: D004583:Electrons; D007306:Insecticides / Q000737:chemistry* / Q000633:toxicity; D015394:Molecular Structure; D012016:Reference Values; D017550:Spectroscopy, Fourier Transform Infrared; D014732:Vibration
chemical_list: D007306:Insecticides