Write the structure of an isomer of compound `C_(4)H_(9)Br` which is most reactive towards `S_(N)1` reaction.

Explanation

`3^(@)` Alkyl halides are most reactive towards `S_(N)1` reaction. Now a `3^(@)` alkyl bromide having `MF" "C_(4)H_(9)Br` is 2-bromo-2-methylpropane, i.e.,
`underset("2-Bromo-2-methylpropane "(3^(@)))(CH_(3)-underset(Br)underset(|)overset(CH_(3))overset(|)(.^(3^(@))C)-Br)`
`therefore`2-Bromo-2-methylpropane is most reactive towards `S_(N)1` reactions.