Question

Which of the following carboxylic acids ha highest acidic strength?

Options

• Chloroacetic acid

• Trichloroacetic acid

• Dichloroacetic acid

• Acetic acid

Answer 1

Trichloroacetic acid

Explanation:

Electron withdrawing group like −Cl, increases. the acidity of carboxylic acid and pK_a value of trichloroacetic acid is very low so stronger is the acid.

Order of increasing acidity:

\[\begin{array}{cc}
\phantom{............}\ce{Cl}\phantom{....................}\ce{Cl}\phantom{..................}\ce{Cl}\phantom{.......}\\
\phantom{.........}|\phantom{......................}|\phantom{....................}|\phantom{.....}\\
\ce{CH3COOH < CH2 - COOH < Cl - CH - COOH < Cl - C - COOH}\\
\phantom{...............................................}|\\
\phantom{................................................}\ce{Cl}
\end{array}\]