Which of the following orders is not correct?

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(B) Let us analyze each option:$(A)$ $o$-toluidine is more basic than $2,6$-dimethylaniline due to the ortho effect,which reduces the basicity of $2,6

Vedclass · Accepted Answer

$- \mathop N\limits^{\oplus} H_3 > - \mathop N\limits^{\oplus} R_3 > - NO_2 > - C \equiv N$ Order of $-I$ effect

Vedclass · Answer

(B) Let us analyze each option:$(A)$ $o$-toluidine is more basic than $2,6$-dimethylaniline due to the ortho effect,which reduces the basicity of $2,6$-dimethylaniline significantly. This is correct.$(B)$ The $-I$ effect order is: $- \mathop N\limits^{\oplus} R_3 > - \mathop N\limits^{\oplus} H_3 > - NO_2 > - C \equiv N$. The given order $- \mathop N\limits^{\oplus} H_3 > - \mathop N\limits^{\oplus} R_3$ is incorrect because alkyl groups are electron-donating ($+I$ effect),which decreases the $-I$ effect of the nitrogen atom compared to hydrogen atoms. Thus,$- \mathop N\limits^{\oplus} R_3$ is actually a stronger $-I$ group than $- \mathop N\limits^{\oplus} H_3$.$(C)$ Aniline is less basic than formamide because the lone pair on nitrogen in aniline is delocalized into the benzene ring,whereas in formamide,it is involved in resonance with the carbonyl group,but the amide nitrogen is generally less basic than aniline due to strong resonance. However,the comparison provided in the image is incorrect as aniline is generally considered more basic than amides in many contexts,but specifically,the order given is incorrect.$(D)$ The acidic strength order is: Formic acid $(pK_a \approx 3.75)$ > Benzoic acid $(pK_a \approx 4.20)$ > Acetic acid $(pK_a \approx 4.76)$. This is correct.Therefore,option $(B)$ is the incorrect order.

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