What is the pKa of 9-Fluorenone?

Answer 1

9-Fluoreneone is different from many ketones as it does not have any acidic protons alpha to the ketone. The only protons available are attached to the aromatic rings, so the pKa would be fairly similar to, perhaps slightly lower than, the pKa of benzene, 43.

Answer 2

The pKa of 9-Fluorenone is typically around 9.4. This means that at a pH below 9.4, it will predominantly exist in its protonated form, while at pH above 9.4, it will be mostly in its deprotonated form.