Monohydrates of Two Isomers of Aminotoluenesulfonic Acid

The structures of 2-aminotoluene-4-sulfonic acid monohydrate, C 7 H 9 NO 3 S.H 2 O (1), and 4-aminotoluene-2-sulfonic acid monohydrate, C 7 H 9 NO 3 S.H 2 O (II), have been determined. The compounds crystallize as zwitterions (ammoniotoluenesulfonate). Both structures consist of layers of nearly planar molecules oriented parallel to one another with the sulfonate and ammonium groups directed towards the adjacent layers. The water molecules lie between the layers. There are hydrogen bonds between the water molecule, sulfonate O atoms and ammonium H atoms in each structure. The structures differ in the stacking pattern of the layers