The conformation of non‐aromatic ring compounds. XLVIII: The crystal structure of trans‐syn‐trans‐2,3,5,6‐tetrachloro‐1,4‐dioxane

Crystals of trans-syn-trans-2,3,5,6-tetrachloro-1,4-dioxane are monoclinic prismatic. The space group is P21/n, a = 6.724, b = 7.552, c = 7.626 A, β = 93.13° and Z = 2. The structure has been solved by Patterson methods and refined by use of integrated photographic copper data measured with a microdensitometer. The molecule has a chair conformation with all chlorine atoms in axial positions and with symmetry ī. Due to steric repulsions by the halogen atoms the chair is rather flat. The mean endocyclic torsional angle is 40°. In agreement with similar observations in other dioxane compounds the C-Cl bond lengths (average value 1.823 A) are rather long.