Haloalkanes And Haloarenes Ques 2

2. In an $S_N 2$ substitution reaction of the type

$R-Br+Cl^{-} \xrightarrow{DMF} R-Cl+Br^{-}$

which one of the following has the highest reactivity rate?

[2008]

(a) $CH_3-CH_2-CH_2 Br$

(b)

(c)

(d) $CH_3 CH_2 Br$

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Answer:

Correct Answer: 2.(d)

Solution:

  1. (d) $S_N 2$ mechanism is followed in case of primary and secondary halides i.e., $S_N 2$ reaction is favoured by small groups on the carbon atom attached to halogens so reactivity order is:

i.e. option (d) is correct.