The correct order of pK a values for the following compounds is:

The correct order of pKa values for the following compounds is:

 

  1. c > a > d > b
  2. b > d > a > c
  3. b > a > d > c
  4. a > b > c > d

Solution

Electron-withdrawing groups increase the acidic nature of the phenol. Nitro group is electron withdrawing group, hence it is the more acidic compound among the given phenols.  

Electron-donating groups decrease the acidic nature where methoxy group is more electron donating, hence less acidic than the iso-propyl group which donates electrons by hyperconjugation effect.

∴ Order of acidic strength is (c) > (a) > (d) > (b)

The order of pKa values are (b) > (d) >(a) > (c).

Asked in: JEE Main 2023 (30 Jan Shift 2)

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