Oxygen with 3 bonds
pKa = <0
Less than zero
Very strong acids
Oxygen with a double bond
pKa = 5 Acetic acid (moderately strong) Oxygen with a double bond
Nitrogens with a positive charge
pKa = 10
Weak acids
Neutral oxygens
pKa = 15
Weak acids
pKa = 25
pKa = 35
pKa = 45
pKa = 50