Which of the following reactions is SN₂ and why?

(i)

(ii)

The reaction (i) is SN₂ reaction because:

⇒ In SN₂ reaction, the attack of the nucleophile occurs from the back side on the α-carbon (carbon carrying the halogen)

⇒ In reaction (i), nucleophile (Y) is attacking from back side. Thus, it undergoes SN₂ reaction.