Q. In a $S_{N} 2$ substitution reaction of the type $R - Br + Cl ^{-} \xrightarrow{D M F}R - Cl + Br ^{-}$ which one of the following has the highest relative rate?
BITSATBITSAT 2013
Solution:
$S_{N} 2$ 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 $CH _{3} CH _{2} Br > CH _{3} CH _{2} CH _{2} Br >$
