A comparative study of the crystal structures of tetrahalogenated hydroquinones and g-hydroquinone.
g-Hydroquinone (1) and its tetrafluoro, tetrachloro and tetrabromo derivs. (2), (3) and (4) adopt crystal structures that have an almost invariant system of O-H...O H bonds. However, within this O-H...O framework, the four structures display variations that are characteristic of the C-H, C-F, C-Cl and C-Br groups. In the parent compd. (1) arom. rings are packed with a herringbone geometry, while in the halogenated derivs. (3) and (4), polarization-type halogen...halogen contacts are optimized. The fluoro deriv. (2) is exceptional in that neither of the above possibilities is adopted, even though the O-H...O scaffolding does not per se prohibit either of them geometrically.
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