Table 2. Basicity of 4,6-Dihydroxypyrimidine Derivatives.

compound	pKb1	pKb2	pKb3
1	0.21;14 0.23;3 0.17 ± 0.01	–6.10;3 −6.24 ± 0.48
2	–0.41 ± 0.03; −0.3014	–7.06 ± 0.37
3	–0.90 ± 0.06	–3.62 ± 0.02	–9.27 ± 0.54
7	–0.03 ± 0.04	–5.81 ± 0.35
8	–6.04 ± 0.32
9	–5.92 ± 0.80
uracil36	–2.38	–7.3 (Ha) ∼ (−12.1 Ho)a
thymine36	–3.02	–6.8 (Ha) ∼ (−10.9 Ho)a

^aAcidity score at the half-protonation point.