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

Alkylhalides have polar C-X bond and undergo nucleophilic substitution reactions. These give a variety of products with nucleophiles such as -OH, -OR, -NH_(2), -CN, -NC, -NO_(2), -ONO, RCOO^(-) , etc. They undergo mainly two types of nucleophilic substitution reactions, S_(N)1 and S_(N)2 . S_(N)1 reactions are two steps reactions which proceed through the formation of carbocations while S_(N)2 reactions are one step reaction which proceeds through the formation of transition state. The stability of carbocation and transition state determine the reactivity of alkyl halides. Write the structure of isomer of compound C_(4)H_(9)Br which is most reactive towards S_(N)1 reaction.

Which one is most reactive towards S_(N)1 reactions ?

Which one is most reactive towards S_(N)1 reactions ?

Which one is most reactive towards S_(N^(1)) reaction?

Which one is the most reactive towards S_(N)1 reaction ?

Which one is most reactive towards S_(N^(1)) reaction?