Reactivity 3 : Electron-pair sharing Unimolecular Nucleophilic Substitution (SN1)

In an SN1 reaction, the rate-determining step involves the departure of the leaving group to form a carbocation. The nucleophile then attacks this carbocation, completing the substitution.

The rate equation for this reaction is: $\text{Rate}=k[\text{substrate}]$ This indicates the reaction is first-order with respect to the substrate, hence the term "unimolecular."