# Is nifedipine a weak base or weak acid?

I was wondering whether someone could explain me if nifedipine is a weak base or a weak acid. I barely can find any information about nifedipine's physicochemical properties in studies, however some suggested that it is a weak acid. If it is a weak acid, which hydrogen atom is dissociable and what would the pKa of that group be?

Nifedipine's structure, as shown on wikipedia:

• Here is a reference which states that the "strongest basic" pKa = 5.33. As for which proton, I'm not sure. – Todd Minehardt May 14 '16 at 15:32
• @ToddMinehardt perhaps the H atom at position 4 of the 1,4-dihydropyridine. – Loong May 14 '16 at 18:10
• My guess is still the N-hydrogen. However a $pK_a$ of 4 is more acidic than I would expect, e.g. in comparison with phtalimide. But there may be higher order effects that affect the acidity. – aventurin May 14 '16 at 19:35