Because the SN1 reaction goes through a flat carbocation, we might expect an optically active starting material to give a completely racemized product. In most cases, however, SN1 reactions actually give more of the inversion product. In general, as the stability of the carbocation increases, the excess inversion product decreases. Extremely stable carbocations give completely racemic products. Explain these observations.
As Carbocation stability increases,the leaving group will be less tightly held by the carbocation for stabilization ; the more stable carbocations are more free in solution meaning more exposed .
More stable carbocations will have longer life times ,allowing the leaving group to drift off in the solvent,leading to more possibility for the incoming nucleophile to attack from the side that the leaving group just left.