Alcohols Phenols and Ethers - Result Question 44
####45. Increasing order of acid strength among $p$-methoxyphenol, $p$-methylphenol and $p$-nitrophenol is
[1993]
(a) $p$-Nitrophenol, $p$-Methoxyphenol, $p$-Methylphenol
(b) $p$-Methylphenol, $p$-Methoxyphenol, $p$-Nitrophenol
(c) $p$-Nitrophenol, $p$-Methylphenol, $p$-Methoxyphenol.
(d) p-Methoxyphenol, $p$-Methylphenol, $p$-Nitrophenol
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Solution:
- (d) Electron-donating groups (- $OCH_3,-CH_3$ etc.) tend to decrease and electron withdrawing groups $(-NO_2)$ tend to increase the acidic character of phenols. Since $-OCH_3$ is a more powerful electron-donating group than $-CH_3$ group, therefore, $p$-methylphenol is slightly more acidic than $p$-methoxyphenol while $p$-nitrophenol is the strongest acid. Thus, option (d), i.e. p-methoxyphenol, $p$-methylphenol, $p$-nitrophenol is correct.
