why does neopentyl chloride not follow Sn2 mechanism?
In neopentyl chloride the leaving group is Chloride (Cl-) ion therefore, the nucleophile will attack the C atom attached to Cl atom from the back side, according Sn2 mechanism. As we know for Sn2 mechanism to proceed the C atom at which the nucleophile will attach itself should be unhindered but in neopentyl this C atom is sterically hindered due to presence of three bulky -CH3 groups which do not allow the nucleophile to approach the C atom to which leaving group is attached. Hence, the Sn2 mechanism is not followed by neopentyl chloride.