An SN1 reaction is a nucleophilic substitution reaction in organic chemistry. It involves substituting one part of a compound with a nucleophile from another compound and occurs in two steps.
SN1 reactions start with an entantiomerically pure reactant and a nucleophile. Next, the nucleophile attacks the reactant and forms a carbocation. The most stable carbocation is formed, so hydride shifts may occur to create a more stable carbocation. Next, the nucleophile attacks the carbocation and adds to the reactant. The final product of an SN1 reaction is a racemic mixture of products. Normally, the R and the S product are formed.