In: Chemistry
Provide an explanation for the difference in Ka between chloroacetic acid and acetic acid
Ka is dissociation constant of acetic acid and chloro acetiacid as followed.
CH3COOH <--------> CH3COO- + H+
Ka = [H+] [CH3COO-] / [CH3COOH]
Acid dissociation constant.
ClCH2COOH <------> ClCH2COO- + H+
Ka = [H+] [CH3COO-] / [ClCH2COOH]
Ka = acid dissociation constant.
The dissociation of proton is more efficient in chloro acetic acid compare to acetic acid. This due to the presence of Cl atom in chloro acetic acid, which can withdraw electron density from alkyl group effectively so the electron density donation from -CH2- group to -CO- group in chloro acetic acid is decreased. so the proton is effectively donated by the -COOH group. Hence the concnetration of [H+] increases and sothat Ka value for chloroacetic acid acts as strong acid compare to acetic acid.