Organic Chemistry Basics 2 Question 57

57. Phenol is less acidic than

(1986)

(a) acetic acid

(b) p-methoxy phenol

(c) $p$-nitrophenol

(d) ethanol

Assertion and Reason

Read the following questions and answer as per the direction given below:

(a) Statement I is correct; Statement II is correct; Statement II is the correct explanation of Statement I

(b) Statement I is correct; Statement II is correct; Statement II is not the correct explanation of Statement I

(c) Statement I is correct; Statement II is incorrect

(d) Statement I is incorrect; Statement II is correct

Show Answer

Solution:

  1. 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 $\longrightarrow$-increasing acid strength $\longrightarrow$