Question

Among the following four compounds
(i) Phenol
(ii) Methyl phenol
(iii) Meta-nitrophenol
(iv) Para-nitrophenol
The acidity order is:

• A. $\left(iv\right)>\left(iii\right)>\left(i\right)>\left(ii\right)$
• B. $\left(iii\right)>\left(iv\right)>\left(i\right)>\left(ii\right)$
• C. $\left(i\right)>\left(iv\right)>\left(iii\right)>\left(ii\right)$
• D. $\left(ii\right)>\left(i\right)>\left(iii\right)>\left(iv\right)$

Answer 1

The correct option is A $\left(iv\right)>\left(iii\right)>\left(i\right)>\left(ii\right)$

In phenols, the presence of electron releasing groups decreases the acidity, whereas presence of electron withdrawing groups increase the acidity, compared to phenol.

Among the meta and para-nitrophenols, the latter is more acidic as the present of - NO${}_2$ group at para position stabilizes the phenoxide ion to a greater extent than when it is present at meta position.

Thus, correct order of acidity is :
$\underset{\left(iv\right)}{Para-nitrophenol}>\underset{\left(iii\right)}{meta-nitrophenol}>\underset{\left(i\right)}{phenol}>\underset{\left(ii\right)}{methylphenol}$