1-{(Z)-1-[3-(4-Bromophenoxy)propoxy]-1-(2,4-difluorophenyl)prop-1-en-2-yl}-1H-1,2,4-triazol-4-ium nitrate

In the title molecular salt, C20H19BrF2N3O2 +·NO3 −, the N atom at position 4 of the heterocyclic ring is protonated. The triazole ring makes dihedral angles of 96.6 (4) and 54.4 (3)° with the 4-bromophenyl and 2,4-difluorophenyl rings, respectively, and the molecule adopts a Z conformation about the C=C double bond. In the crystal, cations and anions are linked by N—H⋯O and C—H⋯O hydrogen bonds.

In the title molecular salt, C 20 H 19 BrF 2 N 3 O 2 + ÁNO 3 À , the N atom at position 4 of the heterocyclic ring is protonated. The triazole ring makes dihedral angles of 96.6 (4) and 54.4 (3) with the 4-bromophenyl and 2,4-difluorophenyl rings, respectively, and the molecule adopts a Z conformation about the C C double bond. In the crystal, cations and anions are linked by N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds.
In the molecular structure of the title compound the double bond has a Z conformation. 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).

Experimental
3 g (0.01 mol) 1-(2,4-difluorophenyl)-2-(1,2,4-triazol)-1-y1)propan-1-one, 10 g of a 50% aqueous sodium hydroxide, 15 ml toluene and 1.5 ml of a 40% aqueous solution of tetrabutyl ammonium hydroxide are mixed and heated to 323.15 K under vigorous stirring. 2.93 g (0.01 mol) 1-bromo-3-(4-bromophenoxy)-propane, dissolved in 10 ml toluene, is instilled into the stirred and warmed solution in the course of 10 h. The mixture is subsequently stirred for another 20 h at 323.15 K. The reaction mixture is mixed with as much water and chloroform so that the aqueous phase becomes lighter than the organic phase. Thereafter, the organic and aqueous phases are separated. The organic phase is dried with sodium sulfate.
The solvents are distilled under reduced pressure. The remaining residue is a dark oil that is diluted with 10 ml 2propanol and then adjusted to a PH-value of 2 by means of 30% aqueous nitric acid. The thus derived nitric acid solution is then cooled in the refrigerator. The impure precipitated product herein is subsequently crystallized from a 1:1 mixture of ethyl acetate and ethanol. The purified product may be analytically identified as an approximately pure Z-isomer of propylene nitrate. Colourless plates of the title compound were obtained by slow evaporation of an ethanol solution.
Details on the synthesis can be found in the literature reported by Ludwig & Kurt (1985).

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

Figure 1
The molecular structure of the title molecule, with displacement ellipsoids drawn at 30% probability levels.

Figure 2
The packing diagram of the title compound. Hydron bonds are shown as dashed lines. 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 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.