. reaction at an asymmetric carbon of a compound always gives
A. an enantiomer of the substrate
B. a product with opposite rotation
C. a mixture of diastereomers
D. a single stereoisomer
Sol: A typical SN2 reaction is shown as
It is evident that only one product is formed, which is not the enantiomer of the substrate. Moreover, it is not necessary that the product has opposite optical rotation than that of the substrate; they differ in configuration only. When the reactant is a stereoisomer, product will also be a single stereoisomer.