Order of acidity of benzoic acid (I), 4-methoxybenzoic acid (II), acetic acid (III) and 4-nitrobenzoic acid…

Order of acidity of benzoic acid (I), 4-methoxybenzoic acid (II), acetic acid (III) and 4-nitrobenzoic acid (IV) is
  1. IV $>$ I $>$ II $>$ III
  2. I $>$ II $>$ IV $>$ III
  3. III $>$ I $>$ II $>$ IV
  4. II $>$ I $>$ IV $>$ III

Solution

An electron-donating group decreases the strength of acids, while electron withdrawing group increases the strength of acids. A methoxy group is clectron donating group, 4-methoxy benzoic acid is a weaker acid than benzoic acid. Nitro group is electron withdrawing group and will increase the strength of acids. Thus, correct order is 4-nitrobenzoic acid (IV) > benzoic acid (I) > 4-methoxy benzoic acid (II) > acetic acid (III)

Asked in: AP EAMCET 2018 (23 Apr Shift 2)

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