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

-benzyl-cinchonidinium bromide, CHNO·Br, with the systematic name ()-(2,4,5)-1-benzyl-5-ethenyl-1-azoniabi-cyclo-[2.2.2]octan-2-yl-methanol bromide, is a quaternary ammonium salt of the 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 alkaloids. In an effort to understand the effects of water on these inter-molecular inter-actions, the structures of anhydrous -benzyl-cinchonidinium bromide, (I), and the sesquihydrate, CHNO·Br·1.5HO, (II), were determined.