Reference pKa Tables
pKa Tables
Estimated reading time: 1 min
In this section
Chapter 3 makes a deliberate choice not to lead with numbers: the goal there is to understand why one acid is stronger than another by evaluating the stability of the conjugate base. This appendix is the reference that goes with that framework — a set of representative pKa values, organized by compound class, to consult once the underlying reasoning is in place.
A caution before using this appendix: the Common Mistake named in Chapter 3 is memorizing pKa values in place of understanding stability. Use this table to check reasoning and to calibrate intuition (is this acid stronger or weaker than water? than acetic acid?) — not as a list to memorize outright. Exact values also vary somewhat by source and solvent; what matters is the relative order and the structural reasoning behind it.
pKa = −log(Ka). A lower pKa means a stronger acid — it dissociates more completely.
Master Table — Representative pKa Values
Ordered from strongest acid to weakest.
Why phenols are more acidic than alcohols (compare phenol, pKa 10, to ethanol, pKa 16): the phenoxide ion delocalizes its negative charge into the aromatic…
Alcohols and water are only weakly acidic — their conjugate bases (alkoxide, hydroxide) carry a full negative charge with no resonance delocalization.…
Ammonium Ions and Amine Basicity
Amines themselves are not usually discussed by “pKa” directly — instead, chemists report the pKa of the conjugate acid (the ammonium ion), often written…
Carbonyl α-Carbons and Enolates
The Four Stability Factors, Revisited
Chapter 3 introduces four factors that stabilize a conjugate base, sometimes remembered by the mnemonic ARIO — Atom, Resonance, Induction, Orbital…