Haloalkanes and Haloarenes Part 1

For any SN1 reaction reactivity is decided by ease of dissociation of alkyl halide
R−X⇌R⊕+X⊕
Higher the stability of R⊕ (carbocation)higher would be reactivity of SN1 reaction
Since stability of cation follows order
CH3−CH2−

⊕

C

⊕

H2
   <CH3−

⊕

C

H−CH2−CH3
     <p−H3CO−C6H4−

⊕

C

H2
Hence correct order is
II < I < III


(OR)


The increasing order of the reactivity of the halides for the SN1 reaction is (II) <(I)< (III).
(II) is primary alkyl halide.
(I) is secondary alkyl halide. Primary alkyl halide is less reactive towards SN1 reaction than secondary alkyl halide.
In (III), the carbocation generated is stabilised due to resonance. Hence, (III) is most reactive towards SN1 reaction.