Tetramethylammonium hydrogen terephthalate

disorder in main residue; R factor = 0.054; wR factor = 0.147; data-to-parameter ratio = 17.0. The asymmetric unit of the title salt, C4H12N +C8H5O4, contains one half of a tetramethylammonium cation and one half of a hydrogen terephthalate monoanion. The N atom of the ammonium cation lies on a twofold rotation axis and the centre of mass of the terephthalate anion is on a centre of inversion. In the crystal, the centrosymmetric terephthalate ions are linked by a very short symmetric O—H O hydrogen bond [O O = 2.4610 (19) Å] into a one-dimensional polymeric chain along [112]. The tetramethylammonium cations and terephthalate anions are then connected through a pair of bifurcated acceptor C—H O hydrogen bonds, generating a three-dimensional supramolecular network. The carboxylate groups at both ends of the terephthalate anion are charge-shared with an equal probability of 0.5. Related literature For a review of very short O—H O hydrogen bonds, see: Speakman (1972). For recent reports of acidic salts of dicarboxylic acids with short intra- and intermolecular O