CRYSTAL AND MOLECULAR-STRUCTURE OF ORGANOPHOSPHORUS INSECTICIDES .17. LEPTOPHOS OXON

The crystal structure of the organophosphorus insecticide leptophos oxon has been determined by three-dimensional X-ray diffraction analysis. The space group for leptophos oxon is Pbca with a = 8.903(2), b = 16.172(5), and c = 21.202(6) Angstrom, and eight molecules in the unit cell. The structure was solved by direct methods and refined by full-matrix least squares to a final discrepancy index of R = 0.052 with 1312 observed reflections [F-0 > 4.0 sigma(F-0)]. For comparison purposes, the charge densities for the phosphorus atom in leptophos and the oxon were calculated with an AM1 Hamiltonian to be 2.575 and 2.689, respectively. Leptophos was calculated to have a Lipid solubility of log P = 5.72; the oxon, log P = 7.00. Due to an interaction between the doubly bonded O and a ring H, the phosphorus in leptophos oxon participates in a third six-membered ring, fixing it closer to the plane of the tetrasubstituted aromatic ring.