Consider the four weak bases listed below. Which would not exist primarily as a cation in aqueous solution at neutral pH? O only aniline, Kb = 4.0 x 10-10, pkg = 4.60 O only morphine, Kb = 1.6 x 10-6, pkg = 8.20 O only caffeine, Kb = 1.4 x 10-4, pKq - 10.1 all will be cationic only quinine, Kb = 3.3 x 106, pkg = 8.52 none will be cationic