Question

Increasing order of acid strength among p-methoxyphenol, p-methylphenol and p-nitrophenol is

• A. p-nitrophenol, p-methoxyphenol, p- methylpheno
• B. p-methylphenol, p-methoxyphenol, p-nitrophenol
• C. p-nitrophenol, p-methylphenol, p-methoxyphenol
• D. p-methoxyphenol, p-methylphenol, p-nitrophenol

Answer 1

Answer: (C)

Since $-N{O}_2$ show strong $-I$ and $-M$ effect, so it is the strongest acid. Between I and II, II is a stronger acid than I because although $-C{H}_3$ shows $+I$ effect and $-OC{H}_3$ show - I effect, but the inductive effect is negligible in para position. Also, $-O-C{H}_3$ group destabilizes the phenolate ions through strong $+$ Meffect. So, $p$ - methoxyphenol is less acidic.