2,5-Dichloroanilinium chloride monohydrate

The title compound, C6H6Cl2N+·Cl−·H2O, is composed of discrete cations, choride anions and water molecules, which are connected through N—H⋯Cl, O—H⋯Cl and N—H⋯O hydrogen bonding. Two H atoms of the positively charged –NH3 + group have two chloride acceptors and the other one has the O atom of the water molecule as acceptor. The chloride anions form hydrogen bonds with two H atoms from two different water molecules and two H atoms from two positively charged –NH3 + groups.

The title compound, C 6 H 6 Cl 2 N + ÁCl À ÁH 2 O, is composed of discrete cations, choride anions and water molecules, which are connected through N-HÁ Á ÁCl, O-HÁ Á ÁCl and N-HÁ Á ÁO hydrogen bonding. Two H atoms of the positively charged -NH 3 + group have two chloride acceptors and the other one has the O atom of the water molecule as acceptor. The chloride anions form hydrogen bonds with two H atoms from two different water molecules and two H atoms from two positively charged -NH 3 + groups.

Comment
The crystal structure of water free 2,5-dichloroanilinium chloride has been reported (Gray & Jones, 2002). We report herein the crystal structure of 2,5-dichloroanilinium chloride monohydrate. The title compound showed interesting H-bonding in its crystal structure (Fig. 1). Two H-atoms of the positively charged NH 3 group have two chloride acceptors and the other H has O atom acceptor of the water molecule, while chloride anions are linked by four-center hydrogen bonds, with each chloride forming H-bonding with two H-atoms, one each from two different water molecules and two H-atoms, one each from two positively charged NH 3 groups. This is in comparison with the usual set of hydrogen bonds from NH 3 to chloride leading to layer structure observed with water free 2,5-dichloroanilinium chloride (Gray & Jones, 2002), with a short Cl1..Cl3 contact. Further, the water free structure involved four weak interactions, namely the three hydrogen bonds H4···Cl3, H6···Cl2 and H3···Cl1 and the chlorine-chlorine interaction Cl2···Cl3. The crystal packing of (I) through N-H···Cl, O-H···Cl and N-H···O hydrogen bonding (Table 1) is shown in Fig.2

Experimental
The solution of pure 2,5-dichloroaniline (0.02 mole) in ethanol (20 cc) was treated dropwise with dilute hydrochloric acid (>0.025 mole) with constant stirring. The resulting mixture was slowly evaporated at room temperature to obtain 2,5-dichloroanilinium hydrochloride monohydrate. The resultant solid was recrystallized to constant melting point from ethanol.
The single crystals used in X-ray diffraction studies were grown in ethanolic solution by slow evaporation at room temperature.

Refinement
H atoms were located in a difference map, and their positional parameters were refined freely except for the water H atoms which were refined with the O-H distances restrained to 0.85 (4) Å and H-H distance restrained to 1.37 (4)Å. All H atoms were refined with isotropic displacement parameters set to 1.2 times of the U eq of the parent atom.   Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.