Crystal structures of 2,6- and 3,5-dichlorobenzoic acids:: nonbonded Cl•••Cl contacts

The crystal structures of 2,6-dichlorobenzoic acid (1) and 3,5-dichlorobenzoic acid (2) were obtained by single-crystal X-ray diffraction. Crystallization of 1 occurred in the centrosymmetric triclinic space group P1 (No. 2) with a = 7.2678(9), b = 9.8543(8), and c = 11.8290(11) Angstrom; alpha = 95.000(7), = 104.262(10), and gamma = 102.128(8)degrees; and Z = 4. Crystallization of 2 occurred in the monoclinic centrosymmetric space group P2(1)/n (No. 14) with a = 3.7812(3), b = 13.996(2), and c = 14.514(2) Angstrom; = 95.183(8); and Z = 4. Chlorine substituents of four dimeric molecules of 2 formed square channels, ca. 3.54 Angstrom on a side, which run parallel to the crystallographic a axis. Monomers of 1 and 2 formed centrosymmetric dimers via near-linear hydrogen bonds. Details of the structures and spectroscopic results are presented and discussed.