The increasing order of acidic strength of th | vedclass

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Question

(A) The acidic strength of phenols depends on the nature of the substituent attached to the benzene ring.Electron-withdrawing groups $(EWG)$ increase

Vedclass · Accepted Answer

$III < I < IV < II$

Vedclass · Answer

(A) The acidic strength of phenols depends on the nature of the substituent attached to the benzene ring.Electron-withdrawing groups $(EWG)$ increase acidic strength by stabilizing the phenoxide ion,while electron-donating groups $(EDG)$ decrease it.$(I)$ $p$-cresol: $-CH_3$ group shows $+I$ and $+H$ effects $(EDG)$.$(II)$ $p$-cyanophenol: $-CN$ group shows strong $-I$ and $-M$ effects $(EWG)$.$(III)$ $p$-methoxyphenol: $-OCH_3$ group shows $+M$ effect (strong $EDG$) and $-I$ effect.$(IV)$ Phenol: No substituent.Comparing the effects: The $-OCH_3$ group in $(III)$ is a stronger electron donor than the $-CH_3$ group in $(I)$ due to the $+M$ effect. Thus,$(III)$ is the least acidic.The order of acidity is: $(III) Therefore,the correct option is $A$.

The increasing order of acidic strength of the given compounds is:

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