Hydrogen bonding in 1:1 protontransfer compounds of 5-sulfosalicylic acid with 4-X-substituted anilines (X = F, CI or Br).

The crystal structures of three proton-transfer compounds of 5-sulfosalicylic acid (3-carboxy-4-hydroxybenzenesulfonic acid) with 4-X-substituted anilines (X = F, Cl and Br), namely 4-fluoroanilinium 5-sulfosalicylate (3-carboxy-4-hydroxyben- zenesulfonate) monohydrate, C₆H₇FN⁺·C₇H₅O₆S¯·H₂O, (I), 4-chloroanilinium 5-sulfosalicylate hemihydrate, C₆H₇C1-N⁺C₇H₅O₆S¯0.5H₂O, (II), and 4-bromoanilinium 5-sulfo-salicylate monohydrate, C₆H₇BrN⁺·C₇H₅O₆S¯·H₂O, (III), have been determined. The asymmetric unit in (II) contains two formula units. All three compounds have three-dimensional hydrogen-bonded polymeric structures in which both the water molecule and the carboxylic acid group are involved in structure extension. With both (II) and (III), which are structurally similar, the common cyclic R²₂(8) dimeric carboxylic acid association is present, whereas in (I), an unusual cyclic R³₃(8) association involving all three hetero- species is found. [ABSTRACT FROM AUTHOR]