4 Rank the reactivity of the following four molecules toward

4) Rank the reactivity of the following four molecules towards S1 reaction from the most reactive one to the least reactive one. CH3Br, CH3OTs, (CH3)CC, (CH3)2CHCI (1) CH3Br > CH3OTs > (CH3)3CCI > (CH3)2CHCI (2) CH3OTs > CH3Br > (CH3)3CCI > (CH3)2CHCI (3) CH3OTs > CH3Br > (CH3)2CHCI > (CH3)3CCI (4) (CH3),CCI (CH3 )2CHCI > CH3OTs >CH3Br 29

Solution

carbocation formation is the rate-determining step in the SN1 mechanism.

so more the stable the cation the faster the reaction will happen.

In SN1 mechanism first, we will check the stability of the carbocation and it the carbocation is same then we will check the leaving group.

we already know that,

carbocation stability:

3⁰ > 2⁰ > 1⁰

Fourth option is the best suitable.

in the case of CH₃OTs and CH₃Br leaving group OTs^- is better leaving group than Br^-.

hence the answer is the fourth option.