The mechanism of the SN1 reaction is shown in the image attached.
The mechanism of SN1 substitution reaction
There are two steps in the mechanism of the SN1 substitution reaction. The first step involves ionizing the alkyl halide substrate in a polar solvent, which causes a carbocation to form and the leaving group to depart. In the second step, a nucleophile attacks the carbocation, which is a reactive intermediate, forming the substitution product.
Interestingly, racemization can result from the nucleophile's ability to attack from either side of the planar carbocation. The stability of the carbocation intermediate affects the reaction rate, which is usually seen when substrates form stable carbocations.