Quinine dihydrochloride hemihydrate

The title compound is a dihydrochloride salt with discrete ionic moieties linked together by extensive hydrogen bonding. Serendipitous water in the lattice aids with the formation of these hydrogen-bonding networks.

Numerous non-covalent interactions link together discrete molecules in the crystal structure of the title compound, 2C 20 H 26 N 2 O 2 2+ Á4Cl À ÁH 2 O {systematic name: 4-[(5-ethenyl-1-azoniabicyclo[2.2.2]octan-2-yl)(hydroxy)methyl]-6-methoxyquinolin-1-ium dichloride hemihydrate}. A combination of hydrogen bonding between acidic H atoms and the anions in the asymmetric unit forms a portion of the observed hydrogen-bonded network.interactions between the aromatic portions of the cation appear to play a role in the formation of the long-range ordering. One ethylene double bond was found to be disordered. The disorder extends to the neighboring carbon and hydrogen atoms.

Structure description
The title salt ( Fig. 1) crystallizes in the P1 space group with four distinct cation-anion pairs in the asymmetric unit and two water molecules. The four compounds form discrete pairs wherein two of the dications are linked together by extensive hydrogen bonding involving the chloride anions. Specifically, moieties A and B are linked through hydrogenbonding networks while C and D are joined to form a second hydrogen-bonded moiety. Within these moiety pairs, distinct hydrogen-bonded chains facilitate the observed packing (Table 1, Fig. 2). For example, hydrogen bonding is observed between the protonated quinuclidine nitrogen and the alcohol group, effectively bridged by a chloride anion making a N-HÁ Á ÁClÁ Á ÁH-O linkage. This interaction is reciprocal between the moieties.
The second major hydrogen-bonded chain is between the protonated quinolinium N-H moieties of the linked pairs. This hydrogen bonding involves a serendipitous water

Synthesis and crystallization
The chloride salt of the quinine was formed via neutralization of the quinine with hydrochloric acid. Hydrochloric acid (2 equiv., 37% w/w) was added to a solution of quinine (1 equiv.) in 25 ml of acetonitrile while stirring. A white crystalline solid formed after the flask is left standing for 4 h. After isolating the product via vacuum filtration, it was (a) The asymmetric unit of the title compound shown with 50% probability ellipsoids. Disorder is omitted for clarity. (b) The asymmetric unit of the title compound colored to define the distinct cation pairs A and B (blue and red) and C and D (yellow and purple) discussed in the manuscript.

Figure 1
Labeling scheme for the cationic portion of the structure. Four distinct dicationic moieties are in the asymmetric unit, labeled using suffixes A, B, C and D. interactions between cationic moieties in the asymmetric unit. Centroid-centroid distances are shown in green.

Figure 3
Packing diagram of the title compound viewed from the (110) plane. Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) x þ 1; y; z; (ii) x þ 1; y À 1; z; (iii) x þ 1; y; z À 1; (iv) x; y À 1; z; (v) x; y; z À 1; (vi) x; y; z þ 1; (vii) x; y þ 1; z; (viii) x À 1; y; z; (ix) x À 1; y þ 1; z; (x) x À 1; y; z þ 1.  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. One ethylene double bond was found to be disordered. The disorder extends to the neighboring carbon and hydrogen atoms. The two disordered moieties were restrained to have a similar geometry as another not disordered equivalent group. Uij components of ADPs for disordered atoms closer to each other than 2.0 Angstrom were restrained to be similar. Subject to these conditions the occupancy ratio refined to 0.505 (9) to 0.495 (9).