Question
With the help of inductive effect, show that monochloroacetic acid is stronger acid than acetic acid.
Solution
This is because chlorine is an electron withdrawing group (-I effect). It withdraws electrons from the carbon chain towards itself. As a result, electron density on the oxygen atoms of O- H bond decreases. This helps in the release of H+ ions and hence acid strength increases. On the other hand, in the case of acetic acid, a methyl group is an electron releasing group (+ I effect). It displaces the electron towards the carbon chain. As a result, electron density on the oxygen atom of O – H bond increases. Therefore, the release of H+ ions become difficult, so acidic character decreases. Hence chloroacetic acid is a stronger acid than acetic acid.
