Chlorouracil (4-Chlorouracil; 6-Chlorouracil) is a halogenated uracil that is useful in studies of the effects of halogenation on nucleic acid base-pair stability and alkali metal ion affinity. Reaction of 6-chlorouracil with 4-(dimethylamino)pyridine, 4-methylpyridine, and pyridin-4-yl-morpholine yielded pyridinium-substituted uracils as chlorides which were converted into pyridinium uracilates by deprotonation. These heterocyclic mesomeric betaines are cross-conjugated and thus possess separate cationic (pyridinium) and anionic (uracilate) moieties. Calculations and X-ray single crystal analyses may be used to characterize these systems and to compare the salts with the betaines.
