Base Ionization Constants in Water at 25 °C

For a weak base B that ionizes in water according to the reaction: B + H2O = BH + OH-, the base ionization constant Kb is defined as
       [BH] [OH-]
 Kb = -------------
        [B]
and pKb = - log Kb


Base name, Formula . . . . pKb
----------- . . . . ----
Ammonia, NH3 . . . 4.752
Aniline, C5H5NH2 . . . 9.37
Hydrazine, H2NNH2 . . . 5.77
Hydroxylamine, NH2OH . . . 7.97
Methylamine, CH3NH2 . . . 3.432
Ethylamine, C2H5NH2 . . . 3.193
Trymethylamine, (CH3)3N . . . 4.20
Quinine, C20H24N2O2 (pKb1) . . . 5.48
(pKb2) . . . 8.97