Features of Hydrogen Bonding
Hydrogen Bonding and acid strength
- In some isomeric carboxylic acids the carboxylate anion in one of them is stabilized through hydrogen bonding thus making it a stronger acid.
- The pKa values of the isomeric carboxylic acids are shown below.
2-hydroxybenzoic
acid
pKa= 2.98
3-hydroxybenzoic acid
pKa= 4.08
4-hydroxybenzoic acid
pKa= 4.58
Only the anion from the ortho-isomer is stabilized through hydrogen bonding thus responsible for greater acidity of the acid. This stabilization is not present in the other isomers due to unfavourable geometry.
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