1. Tardigrade
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  3. Chemistry
  4. Arrange the following organic halides in correct order of reactivity towards SN2 displacement. underset text (P)(CH3)2 C(Br)CH2CH3 , underset text (Q)Br CH2 (CH2)3 CH3 , underset text (R)CH3CH (Br)(CH2)2 CH3

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Q. Arrange the following organic halides in correct order of reactivity towards $SN_2$ displacement.
$\ce{ $\underset{\text{ (P)}}{\ce{(CH_3)2 C(Br)CH_2CH_3 }}$ \; \; , \; \; $\underset{\text{ (Q)}}{\ce{Br CH_2 (CH_2)_3 CH_3 }}$\; \; , \; \; $\underset{\text{ (R)}}{\ce{CH_3CH (Br)(CH_2)_2 CH_3 }}$}$

AP EAMCETAP EAMCET 2019

Solution:

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$3^{\circ}$ alkyl halide (highly sterically hindered)

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$1^{\circ}$ alkyl halide (least sterically hindered)

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$(R) 2^{\circ}$ alkyl halide

Rate of $S _{ N } 2$ reaction $\propto \frac{1}{\text { sterically hindrance }}$

$\therefore $ Rate is $1^{\circ}>2^{\circ}>3^{\circ}$ alkyl halide.

Hence, $Q>\,R>\,P$ is correct answer.