Question

The correct order of acid strength for the following carboxylic acids is:

• A. $I>III>II>IV$
• B. $III>II>I>IV$
• C. $I>II>III>IV$
• D. $II>I>IV>III$

Answer 1

The correct option is C $I>II>III>IV$


Stronger will be the acid when its conjugate base is highly stabilised. (I) is the most acidic and (IV) is the least since $C{O}_2^{-}$ group is attached with a $sp$ hybridised carbon in (I) and with a $s{p}^3$ hybridised carbon in (IV).
(III) is less acidic than (II) as the electron donating group ($-OMe$) destabilises the carboxylate anion by increasing the electron density in the ring.
Hence the order is: $I>II>III>IV$