Which of the following describes a key feature of SN1 reactions?

SN1 reactions are characterized by the formation of a carbocation intermediate. This reaction mechanism proceeds in two main steps: the first involves the departure of the leaving group, which generates a positively charged carbocation. This step is critical since the stability of the carbocation influences the rate of the reaction; more stable carbocations will result in faster SN1 reactions. The second step consists of a nucleophile attacking the carbocation to form the final product.

This formation of a carbocation is what distinguishes SN1 from other substitution mechanisms, such as SN2. In contrast to direct substitution mechanisms or single concerted steps, the SN1 reaction's reliance on an intermediate is what defines its multi-step nature. Furthermore, while nucleophiles do play a role in these reactions, they do not have to be particularly strong, differentiating SN1 further from mechanisms that require strong nucleophiles, such as SN2.