Question

How do you rank SN1 reaction rates?

Answer 1

Concentration of substrate

Explanation:

In a Sn1 reaction the reaction rate does only depend on the concentration of the substrate.
If we for instance have a reaction where we use Br, with a chain on R, reacting with water, we would get the following reaction:

There we have a substrate (as mentioned) which is Br, and a nucleophile "attacking" which is water `H_2O`.
The rate of the reaction is then described as following:

`Rate=k[R-Br]`

For Sn2 reactions the reaction rate would depend on both the substrate and the nucleophile.