Explain stereochemistry of `S_(N)2` reaction with suitable example.

Explanation

In case of optically active alkyl halides, the product formed as a result of `S_(N)2` reaction has the inverted configuration as compared to the reactant. This is because the nucleophile attaches itself on the side opposite to the one where the halogen atom is present. For example, when (-) -2-bromooctane is reacted with sodium hydroxide, (+) -octan-2-ol is formed with the -OH group occupying the position opposite to bromide ion.

Thus, `S_(N)2` reactions of optically active halides are accompanied by inversion of configuration.