1-{(Z)-1-(2,4-Dichlorophenyl)-1-[2-(4-methylphenoxy)ethoxy]prop-1-en-2-yl}-1H-imidazol-3-ium nitrate

In the title salt, C21H21Cl2N2O2 +·NO3 −, the imidazole ring makes dihedral angles of 43.39 (14) and 10.9 (2)° with the 4-methylphenyl and 2,4-dichlorophenyl rings, respectively. The molecule adopts a Z conformation about the C=C double bond, which links the imidazole ring to the 4-methylphenoxy unit via an ethoxy chain. In the crystal, cations and anions are linked into chains by N—H⋯O and C—H⋯O hydrogen bonds.

In the title salt, C 21 H 21 Cl 2 N 2 O 2 + ÁNO 3 À , the imidazole ring makes dihedral angles of 43.39 (14) and 10.9 (2) with the 4methylphenyl and 2,4-dichlorophenyl rings, respectively. The molecule adopts a Z conformation about the C C double bond, which links the imidazole ring to the 4-methylphenoxy unit via an ethoxy chain. In the crystal, cations and anions are linked into chains by N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds.

Experimental
In the molecular structure of the title compound ( Fig. 1) the double bond is Z configurated. In the crystal structure the anions and cations are connected via N-H···O and C-H···O hydrogen bonding (Table 1 and Fig. 2). The bond lengths and bpnd angles in the title compound agree with the corresponding bond lengths and angles reported for a closely related compound (Kurt et al., 1987).

Experimental
1-(2,4-Dichlorophenyl)-2-(1H-imidazol-1-yl)-1-propanone (16.6 g, 0.06 mol), 30% aqueous sodium hydroxide (50 ml), toluene (100 ml) and tetrabutylammonium hydroxide (0.26g, 0.001mol) were mixed and heated to 343.15 K under vigorous stirring. 1-(2-Bromoethoxy)-4-methyl-benzene (13.3 g, 0.06 mol), dissolved in toluene (70 ml), wais instilled into the stirred and warmed solution in the course of 10 h. The mixture was stirred at room temperature, and monitored by TLC until the reaction was complete. The reaction mixture was mixed with as much water and chloroform so that the aqueous phase becomes lighter than the organic phase. Thereafter, the organic and aqueous phases were separated. The organic phase was dried with sodium sulfate. The solvents were distilled under reduced pressure. The remaining residue was a dark oil that is diluted with 100 ml ethanol and then adjusted to a pH-value of 2 by means of 65% aqueous nitric acid. The derived nitric acid solution was cooled in the refrigerator. The impure precipitated product herein was subsequently crystallized from isopropanol. The purified product was analytically identified as an approximately pure Zisomer of propylene nitrate. Crystals of title compound suitable for X-ray diffraction were obtained by slow evaporation of an ethanol solution. Details on the synthesis can be found in the literature (Ludwig & Kurt, 1985).

Refinement
H atoms were positioned geometrically with C-H = 0.93, 0.96 and 0.97 Å for aryl, methyl and methylene H atoms, respectively, and with N-H = 0.86 Å for imidazole H atom, and constrained to ride on their parent atoms, with U iso (H) = 1.5U eq methyl C or 1.2U eq non-methyl C/N).

Figure 1
The molecular structure of the title molecule, with the atom numbering scheme. Displacement ellipsoids are drawn at 30% probability levels.  The packing diagram of the title compound. Hydron bonds are shown as dashed lines. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.33 e Å −3 Δρ min = −0.25 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.034 (5) Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. 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 > 2sigma(F 2 ) is used only for calculating R-factors(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq