Crystal structures of anhydrous and hydrated N-benzyl-cinchonidinium bromide

N-benzyl-cinchonidinium bromide, C₂₆H₂₉N₂O⁺·Br^-, with the systematic name (R)-[(2S,4S,5R)-1-benzyl-5-ethenyl-1-azoniabi-cyclo-[2.2.2]octan-2-yl](quinolin-4-yl)-methanol bromide, is a quaternary ammonium salt of the cinchona alkaloid cinchonidine. This salt is widely used as a chiral phase-transfer catalyst and chiral resolution agent. Both classical and non-classical hydrogen-bonding inter-actions, as well as anion effects have been shown to play key mechanistic roles in the catalysis of cinchona alkaloids. In an effort to understand the effects of water on these inter-molecular inter-actions, the structures of anhydrous N-benzyl-cinchonidinium bromide, (I), and the sesquihydrate, C₂₆H₂₉N₂O⁺·Br^-·1.5H₂O, (II), were determined.