Author:
Dziubek Kamil F.,Katrusiak Andrzej
Abstract
1,4-Dibromobenzene melts at a considerably higher temperature than the 1,2- and 1,3-isomers. This melting-point difference is consistent with the molecular symmetry, as described by Carnelley's rule, and with the frequency of Br...Br halogen bonds. The lowest melting point of 1,3-dibromobenzene correlates with its two symmetry-independent molecules, indicating their inability to pack closely. Single crystals of 1,2- and 1,3-dibromobenzene have been grown under isochoric conditions in a diamond–anvil cell and at isobaric conditions in a glass capillary. Their structures have been determinedin situby X-ray diffraction. At 295 K 1,2-dibromobenzene crystallizes at 0.2 GPa as orthorhombic, space groupPbca,Z′ = 1, and 1,3-dibromobenzene at 0.3 GPa as orthorhombic, space groupP212121,Z′ = 2. The same crystal phases are formed at ambient pressure by freezing these liquids below 256.15 and 248.45 K, respectively. The third isomer, 1,4-dibromobenzene, is a solid at room temperature and crystallizes as monoclinic, space groupP21/a. Striking relations between the structures and melting points of the corresponding dibromobenzene and dichlorobenzene isomers have been discussed.
Publisher
International Union of Crystallography (IUCr)
Subject
Materials Chemistry,Metals and Alloys,Atomic and Molecular Physics, and Optics,Electronic, Optical and Magnetic Materials
Cited by
7 articles.
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