Insecticides. Part II. Crystal structures of 1,1-bis-(p-chlorophenyl)-2,2,2-trichloroethane (p,p′-DDT) and 1-(o-chlorophenyl)-1-(p-chlorophenyl)-2,2,2-trichloroethane (o,p′-DDT)

The crystal structure of 1,1-bis-(p-chlorophenyl)-2,2,2-trichloroethane, (I), was determined from three-dimensional diffractometer data with 900 reflections. Z= 4 in the orthorhombic unit cell, space group Pca2₁ with dimensions, a= 996·3(1), b= 1920·0(2), and c= 788·7(1) pm. The structure was refined by least-squares to R 0·091. The crystal structure of 1-(o-chlorophenyl)-1-(p-chlorophenyl)trichloroethane, (II), was determined from three-dimensional diffractometer data with 2649 reflections by the symbolic addition procedure. Z= 4 in the triclinic unit cell, space group P, with dimensions a= 1201·6(1), b= 1248·1(1), c= 1093·8(1) pm, α= 105·43(3), β= 89·93(3), γ= 109·33(3)°. Least-squares refinement was halted at R 0·048. These two isomers resemble one another. The diameter and projected areas of the two apices and the overall heights are similar but the overall length and distance between the two electronegative centres are not.