Question

Why are $S_{N}1$ reactions generally carried in polar solvents?

Answer 1

A polar protic solvent favours SN1 mechanism because polar solvents has the below properties:

1. It stabilizes the carbocation intermediate. Polar solvents like methanol has a permanent dipole which means that partial negative charge on the molecule will have dipole-dipole interactions with the carbocation, stabilizing it.
2. It reduces the reactivity of the nucleophile. The polar solvent can interact electrostatically with the nucleophile. This reduces the reactivity of the nucleophile and enhances the SN 1 reaction.