Solution:
Higher the tendency to give a proton, higher is the acidic character, and tendency to lose 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-trinitro phenoxide ion which is stabilised by resonance, −1 effect and −M effect, thus is most acidic among the given compounds.
Phenol after losing a proton form phenoxide ion which is also stabilised by resonance, −M and −l effects but is less stabilised as compared to 2,4,6-trinitro phenoxide ions. Thus, it is less acidic as compared to 2,4,6 -
trinitrophenol. (CH3‌COOH) after losing a proton gives acetateion which is stabilised by only resonance. However, it is more resonance stabilised 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 −NO2 groups. Cyclohexanol gives an anion that is least stable among the given,
Hence, the correct order of acidic strength is 2, 4, 6-trinitrophenol > acetic acid > phenol > cyclohexanol
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