Given are cyclohexanol `(I)`, acetic acid `(II),2,4,6-`trinitrophenol `(III)` and phenol `(IV)`. In these the order of decreasing acidic character will be:

Options

A. III gt IV gt II gt I
B. III gt II gt IV gt I
C. II gt III gt I gt IV
D. II gt III gt IV gt I

Answer

B

Explanation

Higher the tendency to give a proton, higher is the acidic character, and tendency to loss a proton depends upon the stability of intermediate, i.e. carbanion formed.
2, 4, 6 - trinitrophenol after the loss of a proton gives 2, 4, 6 - trinitrophenoxide ion which is stabilized by resonance - I effect and - M effect, thus is most acidic among the given compounds.
Phenol after losing a proton form phenoxide ion which is also stabilized by resonance, -M and -I effects but is less stabilized as compared to 2, 4, 6 -trinitrophenoxide ions. Thus, it is less acidic as compared to 2, 4, 6 - trinitrophenol.
Acetic acid` (CH_3COOH)` after losing a proton gives acetate ion which is stabilized by only resonance. However, it is more resonance stabilized as compared to a phenoxide ion, thus more acidic as compared to phenol. 2, 4, 6 - trinitrophenol, however, is more acidic than acetic acid due to the presence of three electron withdrawing `-NO_2` groups.
Cyclohexanol gives an anion that is least stable among the given, thus, it is least acidic
Hence, the correct order is
III>II>IV>I
i.e.
2, 4, 6 - trinitrophenol > acetic acid > phenol > cyclohexanol.