What is the correct increasing order of extent of deprotonation of the following acids in its aqueous solution?
(I) `(CH_3)_2CHCOOH`
(II) `CH_3CH_2COOH`
(III) `Cl_2CHCH_2COOH`
(IV) `CH_3C Cl_2COOH`

Options

A. `II lt I lt III lt IV`
B. `IV lt III lt I lt II`
C. `I lt II lt III lt IV`
D. `I lt IV lt III lt II`

Answer

C

Explanation

Electron withdrawing group `(Cl)` increases acidic strength while electron donating group `(-CH_(3))` decreases acidic strength. Also magnitude of inductive effect decreases drastically on increasing distance. `IV` is stronger acid than `(III)`.

Two methyl group (in I) gives greater `+I` effect than one methyl group (in II), hence I is a weaker acid than II.
Two `-Cl` from closer positon in `IV` exert greater `-I`- effect than the same from large distance in `III`, hence `IV` is stronger acid than `III`.