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

Step-by-step solution

The reactivity of alkyl halides towards the S _ N 1 reaction depends on the stability of the carbocation intermediate formed after the departure of the leaving group. In compound (I), the bromine atom is attached to a bridgehead carbon. The formation of a carbocation at this position is highly unfavorable because the rigid bicyclic structure prevents the carbon from adopting the planar sp^2 geometry required for a stable carbocation (Bredt's rule). Thus, compound (I) is the least reactive. In compound (II), the dep