Benzylamine may be alkylated as shown in the following equation?

C6H5CH2NH2+RXC6H5CH2NHR

Which of the following alkyl halides is best suited for this reaction through SN1 mechanism?

1.CH3Br2.C6H5Br3.C6H5CH2Br4.C2H5Br

Hint: Stability of carbocation

SN1 reaction proceeds through formation of carbocation. Hence, more stable be the carbocation, more reactive is the compound towards SN1 mechanism.
 

Alkyl halides

, Intermediate

a.CH3Brb.C6H5Brc.C6H5CH2Brd.C2H5Br CH3C6HeC6H5CH2( more stable )C2H5
 
Hence, the reaction will proceed through SN1 mechanism when C6H5CH2Br is the substrate because on ionisation it gives a resonance stabilised carbocation (C6H5CH2+).