Question

Which of the following will give $S_{N}1$ reaction quickly?

• A.
• B.
• C.
• D. All of the above at equal rate

Answer 1

The correct option is C

Reactivity of $S_{N}1$ reaction is depends on the stability of the carbocation formed. More the stability of carbocation, more will be its reactivity.
Stability of the carbocation also depends +M/-M effect of the group attached to the carbocation.
In (c), +M group $-OC{H}_3$ increases the stability of the compound and make it most stable than (a) and (b).
Comparing a and b, carbocation formed by (b) will be more stable than formed by (a) due to +R effect of phenyl group.
Stability of carbocation formed by corresponding compound follows the order c>b>a. Hence c give $S_{N}1$ reaction quickly.