JEE Main · 2023 · 11 Apr 2023 · Shift 1 · Haloalkanes and Haloarenes

Where Nu

=

Nucleophile
Find out the correct statement from the options given below for the above 2 reactions.

(A)Reaction (I) is of $2^{nd}$ order and reaction (II) is of $1^{st}$ order
(B)Reaction (I) and (II) both are of $2^{nd}$ order
(C)Reaction (I) is of $1^{st}$ order and reaction (II) is of $2^{nd}$ order✓ Correct
(D)Reactions (I) and (II) both are of $1^{st}$ order

Answer: (C)

Solution

Reaction (I) involves a substrate with an electron-donating group (EDG), which stabilizes a carbocation intermediate. This favors an

S_{N} 1

mechanism, which is first-order (rate depends only on substrate concentration). Reaction (II) involves a substrate with an electron-withdrawing group (EWG), which destabilizes carbocations and makes

S_{N} 1

unfavorable. Instead, it proceeds via an

S_{N} 2

mechanism, which is second-order (rate depends on both substrate and nucleophile concentrations). Therefore, reaction (I) is first-order and reaction (II) is second-order.

JEE Main · 2023 · 11 Apr 2023 · Shift 1 · Single correct option

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JEE Main · 2023 · 11 Apr 2023 · Shift 1 · Haloalkanes and Haloarenes

Solution

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