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)
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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.Keywords:
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Abstract A simple and straightforward method for the preparation of Ta 6 Br 12 cluster compounds is described, The structures of (III) (cubic, space group Fd $\bar 3$ m, Z = 8), (IV) (triclinic, P $\bar 1$ , Z = 2), (V) (triclinic, P $\bar 1$ , Z = 2), and (VI) (orthorhombic, Cmca, Z = 4) are determined by single crystal XRD.
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The title compond, K4[U(C2O4)4]·4H2O, has been prepared in two crystalline modifications; the crystal structures of both have been determined by single-crystal X-ray diffraction methods at 295 K. One form is orthorhombic, space group Fdd2, with unit-cell dimensions a= 30.09(2), b= 22.18(1), c= 12.747(6)Å, and Z= 16; R= 0.043 was obtained for 3 127 'observed' reflections; the other form is triclinic, space group P, with unit-cell dimensions a= 9.595(5), b= 12.998(4), c= 10.329(5)Å, α= 115.47(3), β= 80.49(4), γ= 113.09(13)°, and Z= 2; R= 0.034 for 6 017 independent reflections. In each case, the formula unit is the asymmetric unit; some disorder occurs among the cations in the orthorhombic phase. In both structures the uranium atom is ten-co-ordinate, one of the ligands in each case being bridging and linking the uranium atoms in an infinite one-dimensional polymeric array. For the orthorhombic phase U–O range between 2.37(1) and 2.58(1)Å, while in the triclinic form the range is 2.406(5)–2.641(4)Å. The co-ordination stereochemistries about the uranium atoms are examined in terms of a repulsion model.
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The title compound, C18H14O, is polymorphic at 123 K. The orthorhombic form reported herein has two independent molecules in the asymmetric unit, with molecular volume 313.5 A. The previously reported triclinic (P1) form [Raston & Scott (2000). Green Chem., 2, 49–52] has molecular volume 309.6 A at the same temperature. All three molecules deviate significantly and systematically from the putative Cs symmetry ( r.m.s. = 0.0265, 0.0256, 0.0497 A). Comparison of the two molecules in the orthorhombic polymorph shows that 16 of the 19 equivalent pairs of framework atoms have a mirror-image pattern of deviations (above/below plane), suggesting that the two are quasi-enantiomorphs. The pattern of deviations in the triclinic form is nearly the same (13 of 19 atom pairs) as the orthorhombic form.
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The structure of the triclinic modification of WO3 in terms of the O → W electric dipoles is proposed. In the same way, based on the relationships with the structures of MoO3 and WO2Cl2, the structure of the orthorhombic modification of WO3 is proposed.
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Abstract The hydrothermal treatment of an (NH4)2O/MoO3 mixture at 200 °C (teflon autoclave) yields (NH 4 ) 2 Mo 2 O 7 , (NH 4 ) 8 Mo 10 O 34 and the title compound (NH 4 ) 2 Mo 4 O 13 (I).
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