The correct acidity order of the following is

The correct acidity order of the following is
  1. III $>$ IV $>$ II $>$ I
  2. IV $>$ III $>$ I $>$ II
  3. III $>$ II $>$ I $>$ IV
  4. II $>$ III $>$ IV $>$ I

Solution

A carboxylic acid is stronger acid than phenol, hence both III and IV are stronger acids than both I and II. Also IV has a methyl group that gives electron donating inductive effect and decreases the acid strength. Therefore, III is stronger acid that IV. Between I and II, the dominant electron withdrawing inductive effect of chlorine increases acid strength of phenol slightly, hence II is stronger acid than I. Thus, the overall order is : (a) III $>$ IV $>$ II $>$ I

Asked in: JEE Advanced 2009 (Paper 1)

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