A quasi-diamondoid hydrogen-bonded framework in anhydrous sulfanilic acid.

The title compound (C(6)H(7)NO(3)S) exists as a zwitterion (4-ammoniobenzenesulfonate), +H(3)NC(6)H(4)SO(3)-, and these units are linked into a three-dimensional framework by two distinct two-centre N-H* * *O hydrogen bonds [H* * *O 1.84 and 1.87 A; N* * *O 2.767 (2) and 2.746 (2) A; N-H* * *O 166 and 172 degrees ] and a planar three-centre N-H* * *(O)(2) hydrogen bond [H* * *O 2.03 and 2.37 A; N* * *O 2.816 (2) and 2.877 (2) A; N-H* * *O 162 and 111 degrees; O* * *H* * *O 86 degrees ].