2,4-Dichloroanilinium 4-chlorobenzenesulfonate monohydrate

The asymmetric unit of the title compound, C6H6Cl2N+·C6H4ClO3S−·H2O, contains two 2,4-dichloroanilinium cations, two 4-chlorophenylsulfonate anions and two water molecules. The three H atoms of the positively charged NH3 group have two O atoms of the negatively charged sulfonate anion and one O atom of the water molecule as acceptors. Similarly, the two H atoms of the water molecule have two O atoms of two different negatively charged sulfonate anions as acceptors. Further, one of the O atoms of the sulfonate anion is involved in simultaneous hydrogen bonds with two H atoms, one from the positively charged NH3 group and the other from the water molecule. In the crystal, molecules are packed into a layer structure through N—H⋯O(S), N—H⋯O(H2O) and N—H⋯O(S)⋯H—O(H2O) (three-centre) hydrogen bonding, the chains running along the c axis.

The asymmetric unit of the title compound, C 6 H 6 Cl 2 N + Á-C 6 H 4 ClO 3 S À ÁH 2 O, contains two 2,4-dichloroanilinium cations, two 4-chlorophenylsulfonate anions and two water molecules. The three H atoms of the positively charged NH 3 group have two O atoms of the negatively charged sulfonate anion and one O atom of the water molecule as acceptors. Similarly, the two H atoms of the water molecule have two O atoms of two different negatively charged sulfonate anions as acceptors. Further, one of the O atoms of the sulfonate anion is involved in simultaneous hydrogen bonds with two H atoms, one from the positively charged NH 3 group and the other from the water molecule. In the crystal, molecules are packed into a layer structure through N-HÁ Á ÁO(S), N-HÁ Á ÁO(H 2 O) and N-HÁ Á ÁO(S)Á Á ÁH-O(H 2 O) (three-centre) hydrogen bonding, the chains running along the c axis.
KS thanks the University Grants Commission, Government of India, New Delhi, for the award of a research fellowship under its faculty improvement program.

Comment
The amine and sulfonate moieties are important constituents of many important compounds. As a part of studying the substituent effects on the structures of this class of compounds (Gowda & Kumar, 2003;Gowda et al., 2004Gowda et al., , 2007Shakuntala et al., 2011), in the present work, the crystal structure of 2,4-dichloroanilinium, 4-chlorobenzenesulfonate monohydrate (I) has been determined. The compound (I) showed interesting H-bonding in its crystal structure (Fig. 1). It shows 3-centre H-bonding.
After the initial evolution of hydrogen chloride subsided, the reaction mixture was brought to room temperature and poured into crushed ice in a beaker. The chloroform layer was separated, washed with cold water and allowed to evaporate slowly.
The residual 4-chlorobenzenesulfonylchloride was treated with 2,4-dichloroaniline in the stoichiometric ratio and boiled for ten minutes. The reaction mixture was then cooled to room temperature and added to ice cold water (100 ml). The resultant title compound (I) was filtered under suction and washed thoroughly with cold water. It was then recrystallized to constant melting point from dilute ethanol.
Rod like colorless single crystals used in X-ray diffraction studies were grown in ethanolic solution by slow evaporation at room temperature.

Refinement
The H atoms of the NH groups were located in a difference map and later restrained to the distance N-H = 0.89 (2) Å. The H atoms of the water molecules were located in difference map and were refined with restrained geometry (Nardelli, 1999), viz. O-H distance was restrained to 0.85 (3) Å and H-H distance was restrained to 1.365 Å, thus leading to the angle of 107 Å. The other H atoms were positioned with idealized geometry using a riding model with C-H = 0.93 Å. All H atoms were refined with isotropic displacement parameters (set to 1.2 times of the U eq of the parent atom).