A primary alkyl halide would prefer to undergo:

1.  SN1 reaction     
2.  SN2 reaction    
3.  αElimination  
4.  Racemisation 


(b) A primary alkyl halide would prefer to undergo SN2 reaction.

(a) SN1 reactions occur only if the intermediate carbocation is stable i.e., 3°

carbocation.

(b) SN2 reactions occur if there is less steric hindrance on to the a-carbon of alkyl

halide. in case of primary alky\ halides, carbocation is highly unstable and steric

hinderance is very less. So, primary alkyl halide would prefer to undergo SN2

reaction.

(c) In αelimination, proton and the leaving group are present on same atom.

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