1-Ethyl-4-hydroxy-2,6-dimethylpyridinium bromide dihydrate

# 2007 International Union of Crystallography All rights reserved The title compound, C9H14NO Br 2H2O, comprises 1-ethyl2,6-dimethyl-4-hydroxypyridinium cations and bromide anions, with two solvent water molecules per formula unit. In the crystal structure, the anions, cations and water molecules are linked via intermolecular O—H Br and O— H O hydrogen bonds, forming layers parallel to the (100) plane.


Experimental
The title compound was synthesized by dissolving 1-ethyl-2,6-dimethyl-4(1H)-pyridinone trihydrate (EDMPÁ3H 2 O, 1.51 g) with HBr (2.43 g) in distilled water (5 ml). The solution was stirred well at room temperature for 7 h and the solvent was allowed to evaporate at 323 K. The residual crystalline powder was redissolved in distilled water, and single crystals of (I) were obtained by slow evaporation at 303 K.  Table 1 Hydrogen-bond geometry (Å , ).
The molecular structure of (I), showing displacement ellipsoids drawn at the 50% probability level. H atoms are represented by circles of arbitrary radius.

Figure 2
View of (I) along b, showing layers of organic cations lying parallel to the (100) plane, with Br À anions and water molecules lying between them.
Dashed lines indicate hydrogen bonds. H atoms not involved in hydrogen bonding have been omitted. H atoms, except those of the water molecules, were positioned geometrically with C-H = 0.93 (CH), 0.96 (CH 3 ) or 0.97 Å (CH 2 ), and with O-H = 0.80 Å . They were then refined as riding, with U iso (H) = 1.2U eq (C,O) or 1.5U eq (methyl C). H atoms of the water molecules were found in difference Fourier maps and refined initially with a restrained geometry. In the final cycles of refinement, they were made to ride on their parent O atoms, with U iso (H) = 1.2U eq (O).
Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO (Otwinowski & Minor, 1997); data reduction: DENZO; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97 and PARST (Nardelli 1995  Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > 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.