Question

The carboxylic acid with highest $pK_a$ and lowest $pK_a$ values of the following respectively are:

• A. I, II
• B. I, IV
• C. III, II
• D. III, IV

Hint:

Electron-withdrawing groups decrease \(pK_a\), increasing acidity; electron-donating groups increase \(pK_a\), decreasing acidity.

Answer 1

The Correct Option is D

The carboxylic acid with electron-donating group (III, methyl) has the highest \(pK_a\) (weakest acid), and that with strong electron-withdrawing group (IV, nitro) has the lowest \(pK_a\) (strongest acid).