Final answer:
An optically active primary halide can yield an optically active product when reacting with a nucleophile via an Sn2 mechanism, where the nucleophile attacks from the back, leading to inversion of configuration and preservation of optical activity.
Step-by-step explanation:
The question revolves around whether an optically active primary halide will yield an optically active product after undergoing a substitution reaction. In general, primary alkyl halides follow a mechanism in which the nucleophile attacks the substrate from the back, leading to the expulsion of the leaving group and resulting in the inversion of configuration; this mechanism is known as the Sn2 mechanism. Such reactions are stereospecific and can preserve the optical activity of the molecule if a chiral, non-racemic product is formed.
One classic example is the reaction of a chiral primary halide with a nucleophile such as an oxygen atom from an alcohol in an O-methylation using methyl iodide. The iodide serves as a good leaving group, facilitating the backside attack and inversion of stereochemistry. This results in the creation of a new chiral center, if one was present in the reactant, thus giving an optically active product.