Question

Consider the following chlorides

The correct order of $S{N}_1$ reactivity is

• A. (Q) > (R) > (P)
• B. (Q) > (P) > (R)
• C. (R) > (Q) > (P)
• D. (P) > (Q) > (R)

Answer 1

The correct option is A

(Q) > (R) > (P)

Rate $\propto$ Stability of carbocation formed

So look for stabilization factors. In (Q), post-ionization, the allyl carbocation is stabilized by resonance.

(P) will have to form a highly unstable primary carbocation whereas (R), when undergoing $S_{N}1$, proceeds through a more stable secondary carbocation.