JEE MAIN - Chemistry (2023 - 13th April Evening Shift - No. 12)
Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A : Order of acidic nature of the following compounds is A > B > C.
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Reason R : Fluoro is a stronger electron withdrawing group than Chloro group.
In the light of the above statements, choose the correct answer from the options given below:
Both A and R are correct but R is NOT the correct explanation of A
A is false but R is true
A is true but R is false
Both A and R are correct and R is the correct explanation of A
Explanation
Acidic strength $\alpha-\mathrm{I}$ effect
$$ \alpha \frac{1}{+\mathrm{I}} \text { effect } $$
$\mathrm{F}, \mathrm{Cl}$ exerts $-\mathrm{I}$ effect, Methyl exerts $+\mathrm{I}$ effect, $\mathrm{C}$ is least acidic.
Among $\mathrm{A}$ and $\mathrm{B}$; since inductive effect is distance dependent, Extent of $-\mathrm{I}$ effect is higher in $\mathrm{A}$ followed by $\mathrm{B}$ even though $\mathrm{F}$ is stronger electron withdrawing group than $\mathrm{Cl}$. Thus, $\mathrm{A}$ is more acidic than $\mathrm{B}$.
$$ \alpha \frac{1}{+\mathrm{I}} \text { effect } $$
$\mathrm{F}, \mathrm{Cl}$ exerts $-\mathrm{I}$ effect, Methyl exerts $+\mathrm{I}$ effect, $\mathrm{C}$ is least acidic.
Among $\mathrm{A}$ and $\mathrm{B}$; since inductive effect is distance dependent, Extent of $-\mathrm{I}$ effect is higher in $\mathrm{A}$ followed by $\mathrm{B}$ even though $\mathrm{F}$ is stronger electron withdrawing group than $\mathrm{Cl}$. Thus, $\mathrm{A}$ is more acidic than $\mathrm{B}$.
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