The correct order of reactivity of the given chlorides with acetate in acetic acid is:

The correct order of reactivity for these chlorides with acetate in acetic acid is governed by the

$$S_N1$$

solvolysis mechanism, where the rate-determining step is the departure of the chloride leaving group to form a carbocation intermediate. 3-chloro-4-methylcyclohexene forms a resonance-stabilized secondary allylic carbocation; its ionization is uniquely accelerated by ground-state steric relief (B-strain) between the adjacent bulky

$$-CH_3$$ and $$-Cl$$ groups, making its reaction the fastest. 3-chloro-1-methylcyclohexene lacks this severe ground-state steric strain but forms a highly stable allylic carbocation that benefits from tertiary resonance character, placing it closely second in reactivity. 3-(chloromethyl)cyclohexene ionizes to form a primary carbocation, but it reacts much faster than a typical primary or secondary halide due to significant anchimeric assistance (neighboring group participation) from the adjacent

$$\pi$$-bond, which stabilizes the transition state via a non-classical homoallylic carbocation. Finally, 5-chloro-3-methylcyclohexene forms an isolated, non-allylic secondary carbocation that completely lacks any resonance stabilization or

$$\pi$$-bond assistance, rendering it the least stable intermediate and consequently the least reactive chloride in the series.