N-(2-Bromobenzyl)cinchoninium bromide

The title compound {systematic name: 1-(2-bromobenzyl)-5-ethenyl-2-[hydroxy(quinolin-4-yl)methyl]-1-azabicyclo[2.2.2]octan-1-ium bromide}, C26H28BrN2O+·Br−, is a chiral quaternary ammonium salt of one of the Cinchona alkaloids. The planes of the quinoline and of the bromobenzyl substituent are inclined to one another by 9.11 (9)°. A weak intramolecular C—H⋯O hydrogen bond occurs. The crystal structure features strong O—H⋯Br hydrogen bonds and weak C—H⋯Br interactions.

The oxygen atom (O12), is an acceptor in weak intramolecular hydrogen bonds. The hydrogen bond geometry is given in Table 1.
The disorder of the vinyl groups occurs in almost every molecular structure of Cinchona alkaloids, we have determined.
The vinyl group (i.e. C10 and C11 atoms) is present on the periphery of the whole molecule, so it has ability to move.
The conformation of the vinyl moiety, which we present here, is close to the potential energy minimum and is frequently observed in the structures of erythro Cinchona alkaloids.

Experimental
A mixture of cinchonine (2.95 g, 0.01 mol) and 2-bromobenzylbromide (2.5 g, 0.01 mol) in toluene (40 ml) was stirred and heated at 353 K for 4 h. After cooling to room temperature, hexane (100 ml) was added and the mixture was stirred for 10 h. The precipitated crystals were collected by suction filtration, washed with acetonitrile and dried to give N-(2bromobenzyl)cinchoninium bromide (5.25 g, 97%, m.p. 430 K). Single crystals suitable for X-ray diffraction study were obtained from ethanol by slow evaporation at room temperature.

Refinement
All hydrogen atoms were found on a difference Fourier maps and refined using a riding model with C-H = 0.93Å and U iso (H) = 1.2U eq (C) for aromatic hydrogen atoms, C-H = 0.97Å and U iso (H) = 1.2U eq (C) for methylene groups and C-H = 0.98Å and U iso (H) = 1.2U eq (C) for methine groups. The O based atom H12 was refined with U iso (H) = 1.2U eq (O).

Figure 1
The asymmetric unit of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes.