Question

Which of the following orders regarding the acidic strength of phenols is correct?

• A. p-nitrophenol > p-amino phenol > p-chloro phenol
• B. p-amino phenol > p-nitro phenol > p-chloro phenol
• C. p-amino phenol > p-chloro phenol > p-nitro phenol
• D. p-amino phenol < p-chloro phenol < p-nitro phenol

Answer 1

The correct option is D p-amino phenol < p-chloro phenol < p-nitro phenol

Relative Inductive effects, in decreasing order of -I effect is
$-N{H}_3^{+}>-N{O}_2>-S{O}_{2}R>-CN>-S{O}_{3}H>-CHO>-CO>-COOH$
$>-COCl>-CON{H}_2>-F>-Cl>-Br>-I>-OR>-OH$
$>-N{H}_2>-C_6{H}_5>-CH=C{H}_2>-H$
The strength of inductive effect is also dependent on the distance between the substituent group and the main group, the greater the distance the weaker the effect.
From the given options, as it can be seen by the order of -I given above, the acidic strength is more for a more -I effect causing substituent, hence the correct option is (D).
p-aminophenol < p-chloro phenol < p-nitrophenol.