Question

The increasing order of the reactivity of the following halides for the ${\mathrm{S}}_{\mathrm{N}}1$ reaction is :

• A. $\left(\mathrm{I})<(\mathrm{III})<(\mathrm{II}\right)$
• B. $\left(\mathrm{II})<(\mathrm{III})<(\mathrm{I}\right)$
• C. $\left(\mathrm{III})<(\mathrm{II})<(\mathrm{I}\right)$
• D. $\left(\mathrm{II})<(\mathrm{I})<(\mathrm{III}\right)$

Answer 1

The correct option is D

$\left(\mathrm{II})<(\mathrm{I})<(\mathrm{III}\right)$

The correct options are (d)

The Explanation for the correct options:

(d)

• Explanation: The halides' reactivity in ascending order for the ${\mathrm{S}}_{\mathrm{N}}1$reaction is$\left(\mathrm{II})<(\mathrm{I})<(\mathrm{III}\right)$.\
• $\left(\mathrm{II}\right)$an primary alkyl halide $\left(\mathrm{I}\right)$is a secondary alkyl halide.
• The reactivity of a primary alkyl halide towards ${\mathrm{S}}_{\mathrm{N}}1$reaction is less than a secondary alkyl halide.
• In$\left(\mathrm{III}\right)$, Due to resonance, the carbocation that is produced is stabilized. Hence, $\left(\mathrm{III}\right)$ is most reactive to the ${\mathrm{S}}_{\mathrm{N}}1$reaction.

The correct option is (d): The halides' reactivity in ascending order for the ${\mathrm{S}}_{\mathrm{N}}1$reaction is$\left(\mathrm{II})<(\mathrm{I})<(\mathrm{III}\right)$.