Which of the following is least reactive towards SN $^{1}$ reactions?

Which of the following is least reactive towards SN $^{1}$ reactions?
  1. $\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{Br}$
  2. $\mathrm{CH}_{3}-\mathrm{CH}(\mathrm{Br})-\mathrm{CH}_{3}$
  3. $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}-\mathrm{Br}$
  4. $\mathrm{CH}_{3}-\mathrm{Br}$

Solution

Order of reactivity in alkyl halides towards $\mathrm{SN}^{\prime}$ reaction is : Tertiary > Secondary > Primary

Asked in: MHT CET 2020 (19 Oct Shift 2)

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