Dissociation of acids

Substituent effects on acidity

Simple acids

Acid	pKa
Acetic acid	4.5
Hydroxyacetic acid (glycolic acid)	3.83
Chloroacetic acid	2.85
Dichloroacetic acid	1.48
Trichloroacetic acid	0.70
Trifluoroacetic acid	0.23
[H3O+ ]	[-1.5]

Substituted Benzoic Acids

p-Methoxybenzoic (Y= O-CH3)	4.66
Benzoic (Y= H)	4.54
p-Nitrobenzoic (Y= NO2)	3.73