SYNTHESIS AND CRYSTALLOGRAPHY OF 2 HEXACHLORO-NAPHTHALENES .2. 1,2,4,5,6,8-HEXACHLORO-NAPHTHALENE AND 1,2,4,5,7,8-HEXACHLORONAPHTHALENE

1,2,4,5,6,8-Hexachloronaphthalene (3) and 1,2,4,5,7,8-hexachloronaphthalene (6) have been synthesized by chlorination of 1,5-dinitronaphthalene and 1,8-dinitronaphthalene to 3,4,7,8-tetrachloro-1,5-dinitronaphthalene and 3,4,5,6-tetrachloro-1,8-dinitronaphthalene, respectively. The nitro groups were then replaced by chlorine atoms in one step according to the Ponomarenko reaction. Crystal and molecular structures of the two title isomers were determined by single-crystal X-ray diffraction methods. Two similar, centrosymmetric molecules were found for 3 while two similar molecules not connected by any symmetry element in the space group were found for 6. Both molecules of 3 were planar, whereas one of the two molecules of 6 was planar and the other one was slightly distorted. The hexachloronaphthalenes 3 and 6 crystallized in the space group P2(1)/c and P2(1)/a, respectively, with the following cell dimensions: 3, a = 17.568(5), b = 3.853(2), c = 18.564(6) and beta = 117.14(2)-degrees; 6, a = 18.553(13), b = 3.882(2), c = 31.55(2) and beta = 94.74(5)-degrees. The structures were determined by direct methods and the obtained models, containing a total of 97 parameters for 3 and 189 parameters for 6, were refined by full-matrix least-squares calculations that gave a final R value of 0.055 for 527 unique reflections with I greater-than-or-equal-to 2sigma (I) for 3, and 0.075 for 1257 unique reflections with I greater-than-or-equal-to 2sigma (I) for 6.