title: 8-Ammonio-naphthalene-2-sulfonate monohydrate: the zwitterionic hydrate of 1,7-Cleve's acid.
abstract: The structure of 8-amino-2-naphthalene-sulfonic acid monohydrate (1,7-Cleve's acid hydrate), C(10)H(9)NO(3)S·H(2)O, shows the presence of a sulfonate-aminium group zwitterion, both groups and the water mol-ecule of solvation giving cyclic R(3) (3)(8) O-H⋯O and N-H⋯O inter-molecular hydrogen-bonding inter-actions, forming chains which extend down the a axis of the unit cell. Additional peripheral associations, including weak aromatic ring π-π inter-actions [centroid-centroid distance = 3.6299 (15) Å], result in a two-dimensional sheet structure.
authors.forename: Graham
authors.initials: G
authors.lastname: Smith
authors.forename: Urs D
authors.initials: UD
authors.lastname: Wermuth
authors.forename: David J
authors.initials: DJ
authors.lastname: Young