Novel, predicted patterns of supramolecular self-assembly, afforded by tetrameric R-4(4)(12) rings of C-2 symmetry in the crystal structures of 2-hydroxy-1-cyclopentanecarboxylic acid, 2-hydroxy-1-cyclohexanecarboxylic acid and 2-hydroxy-1-cycloheptanecarboxylic acid

Determination of the crystal structures of the homologous (1R*,2R*)-trans-2-hydroxy-1-cyclopentanecarboxylic acid (5T), (1R*,2S*)-cis-2-hydroxy-1-cyclohexanecarboxylic acid (6C) and (1R*,2S*)-cis-2-hydroxy-1-cycloheptanecarboxylic acid (7C) proved a predicted pattern of supramolecular close packing. The prediction was based on the common features observed in the crystal structures of six related 2-hydroxy-1-cyclopentanecarboxylic acids and analogous carboxamides [Kalman et al. (2001). Acta Cryst. B57, 539-550]. This pattern is characterized by tetrameric R-4(4)(12) rings of C-2 symmetry formed from dimeric R-2(2)(12) rings. The C-2 symmetry of such tetramers is not common in the literature, usually they have C-i symmetry. Both types of tetramers are formed from dimers with similar or opposite orientation. The R-2(2)(12) dimers differ in their hydrogen bonds. In 5T the monomers are joined by a pair of O1-H ... O2=C bonds, whereas in 7C they are joined by a pair of O3-H...O1-H bonds. In 6C 60% of the disordered R-2(2)(12) dimers are similar to those in 7C, while 40% resemble those in 5T. Apart from these hydrogen-bonding differences and the ring-size differences, the three crystals exhibit isostructurality.