Organic Chemistry Basics - Result Question 105
57. Phenol is less acidic than
(a) acetic acid
(b) p-methoxy phenol
(c) $p$-nitrophenol
(d) ethanol
(1986)
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Answer:
Correct Answer: 57. (a, c)
Solution:
- Phenol is less acidic than a carboxylic acid (acetic acid). Nitro group from para position exert electron withdrawing resonance effect, increases acid strength. Therefore, phenol is less acidic than $p$-nitro phenol.
On the other hand, methoxy group from para position, donate electrons by resonance effect, decreases acid strength of phenol. Also ethanol is weaker acid than phenol due to resonance stabilisation in phenoxide ion.
Hence,
ethanol < p -methoxyphenol < phenol < p -nitrophenol < acetic acid
——- increasing acid strength $ \longrightarrow $
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