Question

Which of the following represents the correct order of the acidity in the given compounds?

पर्याय

• FCH₂COOH > CH₃COOH > BrCH₂COOH > ClCH₂COOH

• BrCH₂COOH > ClCH₂COOH > FCH₂COOH > CH₃COOH

• FCH₂COOH > ClCH₂COOH > BrCH₂COOH > CH₃COOH

• CH₃COOH > BrCH₂COOH > ClCH₂COOH > FCH₂COOH

Answer 1

FCH₂COOH > ClCH₂COOH > BrCH₂COOH > CH₃COOH

Explanation:

Electron withdrawing substituent (like a halogen, −NO₂, C₆H₅ etc.) would disperse the negative charge and hence stabilise the carboxylate ion and thus increase the acidity of the parent acid. On the other hand, electron-releasing substituents would intensify the negative charge, destabilise the carboxylate ion and thus decrease the acidity of the parent acid.

Electronegativity decreases in order:

F > Cl > Br

and hence, the −I effect also decreases in the same order; therefore, the correct option is:

FCH₂COOH > ClCH₂COOH > BrCH₂COOH > CH₃COOH