8-Hydroxy-5,7-dimethylquinolin-1-ium hydrogen sulfate

The quinoline ring system of the title salt, C11H12NO+·HSO4 −, is essentially planar, with a maximum deviation of 0.054 (2) Å for all non H atoms. In the crystal, the cations and anions are linked via N—H⋯O, O—H⋯O and weak C—H⋯O hydrogen bonds, and are stacked respectively in columns along the a axis. π–π stacking interactions, with centroid–centroid distances of 3.5473 (12) and 3.6926 (12) Å, are also observed. The crystal studied was an inversion twin with refined components of 0.43 (7):0.57 (7).

The quinoline ring system of the title salt, C 11 H 12 NO + ÁHSO 4 À , is essentially planar, with a maximum deviation of 0.054 (2) Å for all non H atoms. In the crystal, the cations and anions are linked via N-HÁ Á ÁO, O-HÁ Á ÁO and weak C-HÁ Á ÁO hydrogen bonds, and are stacked respectively in columns along the a axis.stacking interactions, with centroidcentroid distances of 3.5473 (12) and 3.6926 (12) Å , are also observed. The crystal studied was an inversion twin with refined components of 0.43 (7):0.57 (7).  Markees et al. (1970). For related structures, see: Loh et al. (2010a,b). For bond-length data, see: Allen et al. (1987). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986).
The asymmetric unit of the title compound ( Fig. 1) consists of one 8-hydroxy-5,7-dimethylquinolin-1-ium cation and one hydrogen sulfate anion. One proton is transferred from the hydroxyl group of sulfuric acid to the atom N1 of 8-hydroxy-5,7-dimethylquinoline during the crystallization, resulting in the formation of salt. The quinoline ring system (C1-C9/N1) is essentially planar with a maximum deviation of 0.054 (2) Å at atom C8. The bond lengths (Allen et al., 1987) and angles are normal.

Experimental
A few drops of sulfuric acid were added to a hot methanol solution (20 ml) of 8-hydroxy-5,7-dimethylquinoline (36 mg, Aldrich) which had been warmed over a heating magnetic stirrer hotplate for a few minutes. The resulting solution was allowed to cool slowly at room temperature and crystals of the title compound (I) appeared after a few days. Å) and were refined using a riding model, with U iso (H) = 1.2 U eq (C) or 1.5U eq (methyl C). A rotating-group model was used for the methyl group. The crystal studied was an inversion twin, with a ratio of the twin components of 0.43 (7):0.57 (7). The Hooft y parameter was 0.48 (4).

Figure 1
The molecular structure of the title compound with atom labels with 50% probability displacement ellipsoids.

Figure 2
The crystal packing of the title compound. The H atoms not involved in the intermolecular interactions (dashed lines) have been omitted for clarity.  (7) Special details Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. 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.