The p K(a)'s of the 6-CH groups of N-methyl-2-methoxypyridinium, N-methyl-4-methoxypyridinium, and 1-methyl-2,4-dimethoxypyrimidinium ions in aqueous solution were determined to be about 33. The p K(a) values were nearly identical to each other and surprisingly similar to those reported for the neutral pyridones and uracil. Further determination of the enthalpies and entropies of the H-D exchange reactions revealed the role of solvation.

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