N&PD Moderators: Skorpio | thegreenhand
pKa (not PKa)
can be found searching the parent molecule and not the salt itself, like, searching for pKa of tartaric acid, and for the drug molecule.
Even though you can't find, it can be approximated depending on functional group and adjacent atoms
and, If your molecule is stable to acid and base, it is OK to use "too much" acid and base during A/B, actually some excess amount should be used in conventional A/B (not drug related)