Predict the stereochemistry of the product formed if an optically active alkyl halide undergoes substitution reaction by S N 1 mechanism.

In S N 1 mechanism, there are two steps. The first involves the formation of intermediate carbocation by heterolysis of tertiary compound. This intermediate carbocation contains sp 2 hybridized carbon atom and thus it is planar. In the second step carbocation is attacked by the nucleophile from either side of R + so that a racemic mixture is formed in which the optical activity due to one is opposite of the other. Hence, an optically inactive product is formed when an optically active alkyl halide undergoes substitution reaction by S N 1 mechanism.