Hydroxypyrimidines

The preparation of hydroxypyrimidines must be divided into two categories, pyrimidinones (2- or 4/6-hydroxypyrimidines) and pyrimidinols (5- or extranuclear hydroxypyrimidines) simply because the approaches are different. 

Repeat your analysis for tautomeric equilibria between 4-hydroxypyridine and 4-pyridone, 2-hydroxypyrimidine and 2-pyrimidone and 4-hydroxypyrimidine and 4-pyrimidone. For each, identify the favored (lower-energy) tautomer, and then use equation (1) to calculate the ratio of tautomers present at equilibrium. Point out any major differences among the four systems and rationalize what you observe. (Hint Compare dipole moments and electrostatic potential maps of the two pyridones and the two pyrimidones. How are these related to molecular stability )... 

---