Organic Chemistry Basics 2 Question 14
14. The correct order of acidity for the following compounds is
(2016 Adv.)
I
III
II
(a) I $>$ II $>$ III $>$ IV
(b) III $>$ I $>$ II $>$ IV
(c) III $>$ IV $>$ II $>$ I
(d) I $>$ III $>$ IV $>$ II
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Answer:
Correct Answer: 14. (a)
Solution:
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- OH group displays both kinds of effect; an electron withdrawing acid-strengthening inductive effect from the meta-position and an electron-releasing acid weakening resonance effect from the para-position (at this position, resonance effect overweighs the inductive effect).
Thus, III > IV.
$o$-hydroxybenzoic acid (II) is far stronger than the corresponding meta and para isomers as the carboxylate ion is stabilised by intramolecular H-bonding.
2,6-dihydroxybenzoic acid (I) forms carboxylate ion which is further stabilised by intramolecular H-bonding, Thus, correct order is
