The fastest SN1 reaction is of the followings:
1
MeO - CH2 - Cl
2
Me - CH2 - Cl
3
\(\begin{array}{*{20}{c}} \rm O \ \ \ \ \ \ \ \ \ \\ {||} \ \ \ \ \ \ \ \ \ \\ {\rm Me - C - CH - Cl} \end{array}\)
4
Ph - CH2 - CH2 - Cl
The fastest SN1 reaction is of the followings: