Question

The correct order of increasing pKa values of the compounds:
(A) CH$_3$COOH
(B) CH$_2$OCH$_2$COOH
(C) Cl$_3$COOH
(D) (CH$_3$)$_3$CCOOH
Choose the correct answer from the options given below:

• A. A $<$ B $<$ C $<$ D
• B. A $<$ C $<$ B $<$ D
• C. B $<$ A $<$ C $<$ D
• D. C $<$ B $<$ A $<$ D

Answer 1

Answer: (A)

A $<$ B $<$ C $<$ D

Answer 2

The pKa value is inversely related to the strength of an acid. Trichloroacetic acid (Cl$_3$COOH) is the strongest acid with the lowest pKa due to the electron-withdrawing effect of the chlorine atoms. Glycolic acid (CH$_2$OCH$_2$COOH) is more acidic than acetic acid (CH$_3$COOH) due to its ability to stabilize the conjugate base. The bulky tert-butyl group in (CH$_3$)$_3$CCOOH decreases acidity, giving it the highest pKa.