Why do we get slightly more inversion product than retention product in SN1 reaction?

Question

Theoretically, in $\\mathrm{S_N1}$ reaction we should get a racemic mixture as the product because the nucleophile can attack from either side of the formed carbocation. However, many textbooks claim that there's slightly more inversion product than retention product. Is there any specific reason for this to happen.

Answer 1

It may have to do with the structure and reactivity of the carbocation. Although theoretically planar, the carbocation might be more sterically hindred from the front side; also very reactive carbocations may react so fast that the leaving group is not completely removed from the area, and rear approach by the nucleophile preferably happens. There are several factors to consider: the size and reactivity of the carbocation,, the size and reactivity of the nucleophile, the solvent, the temperature, and concentrations.