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Find the relative acid strengths in the following groups: (a) phenol, m-chlorophenol, m-nitrophenol, m-cresol (b) phenol, benzoic acid, p-nitrophenol, carbonic acid (c ) phenol, p-chlorophenol, p-nitrophenol, p-cresol (d) phenol, o-nitrophenol, m-nitrophenol, p-nitrophenol (e) phenol, p-chlorophenol, 2,4,6-trichlorophenol, 2,4-dichlorophenol (f) phenol, benzyl alcohol, benzenesulphonic acid, benzoic acid |
Answer» Solution :(a) m-chlorophenol `LT` m-nitrophenol `lt` m-cresol `lt` phenol  Nitro GROUP has + on N, it has a greater electron - withdrawing inductive effect than has Cl. The decreasing order of relative acid strengths Benzoic acid `gt` CARBONIC acid `gt` p-nitrophenol `gt` phenol (b) The decreasing order of relative acid strengths Benzoic acid `gt` carbonic acid `gt` p-nitrophenol `gt` phenol (c ) The resonance effect of `p-NO_(2)` exceeds the inductive effect of `p-Cl. p-CH_(3)` is electron releasing. The decreasing order of relative acid strengths p-nitrophenol `gt` p-chlorophenol `gt` phenol `gt` p-cresol (d) Intramolecular H-bonding makes the o-isomer weaker than the p-isomer. The increasing order of relative acids strengths p-nitrophenol `gt` o - nitrophenol `gt` m - nitrophenol `gt` phenol (e) The decreasing order of relative acids strengths 2,4,6 - trichlorophenol `gt` 2,4 - dischlorophenol `gt` p-chlorophenol `gt` phenol (f) Benzyl alcohol `lt` phenol `lt` benzoic acid `lt` benzene sulphonic acid The decreasing order of relative acid strengths Benzene sulphonic acid `gt` benzoic acid `gt` phenol `gt` benzyl alcohol |
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