Which reaction is not possible?

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Question

(D) The acidity order of the conjugate acids is: $CH_3-OH > CH_3-C \equiv C-H > CH_3-NH_2 > CH_4 > CH_2=CH_2$. An acid-base reaction is possible if a

Vedclass · Accepted Answer

$CH_2=CH_2 + CH_3-Li \rightleftharpoons CH_2=CH^-Li^+ + CH_4$

Vedclass · Answer

(D) The acidity order of the conjugate acids is: $CH_3-OH > CH_3-C \equiv C-H > CH_3-NH_2 > CH_4 > CH_2=CH_2$. An acid-base reaction is possible if a stronger acid reacts with a stronger base to form a weaker acid and a weaker base. In option $D$,$CH_2=CH_2$ is a much weaker acid $(pK_a \approx 44)$ than $CH_4$ ($pK_a \approx 50$ is incorrect,actually $CH_4$ is $pK_a \approx 50$ and $CH_2=CH_2$ is $pK_a \approx 44$,but the reaction requires the conjugate acid of the base to be weaker than the reactant acid). Specifically,$CH_3^-$ is a much stronger base than $CH_2=CH^-$. Therefore,the reaction $CH_2=CH_2 + CH_3^- \rightarrow CH_2=CH^- + CH_4$ is not feasible as it would produce a stronger base from a weaker one.

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