STRUCTURES OF THE CHOLINE ION IN DIFFERENT CRYSTAL SURROUNDINGS

The crystal structures of four choline salts have been determined: choline (S)-N-acetylserinate, C5H14NO+.C5H8NO4-, choline (R,R)-hydrogentartrate, C5H14NO+.C4H5O6-, choline (+/-)-N-acetylphenylalaninate, C5H14NO+.C11H12NO3-, and dicholine phthalate, 2C5H14NO+.C8H4O42-. In these compounds the choline ion adopts two different conformations, extended and folded, both of which are low-energy conformations. In all four crystal structures, the hydroxy group of the choline ion is involved in a hydrogen bond to a carboxylate group. Short contacts between the quaternary ammonium groups and the carboxylate-groups are not observed, but there are many weak contacts.