Question

A primary alkyl halide would prefer to undergo..........

(a) $S_{N}1$ reaction (b) $S_{N}2$ reaction (c) $\alpha -$ elimination (d) racemisation

Answer 1

Answer: (b). A primary alkyl halide would prefer to undergo $S_{N}2$ reaction.

(a) $S_{N}1$ reaction occur only if the intermediate carbocation is stable i.e., $3^{\circ }$ carbocation.

(b) $S_{N}2$ reaction occur if there is less steric hinderance on to the $\alpha -$carbon of alkyl halide. In case of primary alkyl halides, carbocation is highly unstable and steric hinderance is very less. So, primary alkyl halide would prefer to undergo $S_{N}2$ reaction

(c) In $\alpha -$ elimination, proton and the leaving group are present on same atom.

(d) Racemisation is the process of conversion of enantiomer into a racemic mixture.