JEE Chemistry 2023 Question with Solution

Given: Two reactions are shown, one with an electron-donating group $-OCH_3$ and one with an electron-withdrawing group $-NO_2$.

Find: The correct order of reaction (I) and reaction (II).

The solution states that the reaction involving an electron-donating group like $-OCH_3$ increases electron density and makes reaction (I) proceed by a first-order mechanism.

It further concludes that reaction (II) also involves a $1^{\text{st}}$ order mechanism, and explicitly states: "Thus, the correct answer is (3): Reaction (I) is of $1^{\text{st}}$ order and reaction (II) is of $1^{\text{st}}$ order."

Therefore, the correct option is C.

Note: The explanatory image labels the electron-withdrawing group case as $S_N2$ and $2^{\text{nd}}$ order, but the written conclusion on the solution declares both reactions to be first order. As per the provided the solution authority, the final marked answer is taken as C.

Given:

• Electron-donating group case: $-OCH_3$
• Electron-withdrawing group case: $-NO_2$

Find: Which option matches the reaction orders.

From the extracted explanation:

1. For reaction (I), the electron-donating group $-OCH_3$ increases electron density, leading to a faster nucleophilic attack.
2. The solution text says this makes reaction (I) $1^{\text{st}}$ order.
3. For reaction (II), the text first mentions a $2^{\text{nd}}$ order mechanism in discussion, but then states that reaction (II) involves a $1^{\text{st}}$ order mechanism.
4. The final conclusion on the page is:

Hence, the correct option marked on the source is C.