Question

Which of the following substituents will decrease the acidic strength of phenol?

• A. $-N{O}_2$
• B. $-CN$
• C. $-C{H}_3$
• D. $-CHO$

Answer 1

Answer: (C)

$-C{H}_3$

Acidic strength of phenol is enhanced by the presence of electron- withdrawing groups which stabilized the pheoxide ion. On the other hand, presence of electron- donating group destabilizes the phenoxide ion, thus decreasing the acidic strength. Hence, $-C{H}_3$ will decrease the acid strength of phenol. Since, it is an electron donating group.