Identify the correct order of reactivity for the S _ N 1 reaction among the following compounds: (I) (II) (III)

Step-by-step solution

The reactivity of a compound in an S _ N 1 reaction depends on the stability of the intermediate carbocation formed after the departure of the leaving group ( Br ⁻ ). 1. Compound (I) forms the cyclopentyl cation. This is a secondary, non-aromatic carbocation and is relatively stable. 2. Compound (II) forms the cyclopentadienyl cation. This cation has a continuous cyclic conjugated system with 4 electrons. According to Hückel's rule, it is antiaromatic and therefore highly unstable. 3. Compound (III) forms the 5-met