Organic Chemistry for Dummies 2nd Edition by Arthur Winter, PhD
The orbital on which the lone-pair anion rests also affects the acidity.
Electron-withdrawing groups on an acid also stabilize the conjugate base anion by allowing some of the charge on the anion to delocalize to other parts of the molecule.
Acids with conjugate bases that allow the negative charge to be delocalized through resonance are stronger acids than acids whose conjugate bases don’t have resonance structures.
Weak acids and bases are lower in energy than strong acids and bases,
==Example:== Predict the direction of the acid-base reaction between hydrogen cyanide (HCN) and acetate (C2H3O2–)
If you know the pKa values of the two acids on both sides of the equation, equilibrium will favor the side with the acid that has the highest pKa.