There are two simple ways in which the SN2 reaction of methyl chloride could occur with hydroxide ion; they differ in the direction of approach of the reagents. The hydroxide ion could attack chlorom...There are two simple ways in which the SN2 reaction of methyl chloride could occur with hydroxide ion; they differ in the direction of approach of the reagents. The hydroxide ion could attack chloromethane at the front side of the carbon where the chlorine is attached or, alternatively, the hydroxide ion could approach the carbon on the side opposite from the chlorine in what is called the back-side approach. The stereochemical consequences of front- and back-side displacements are different.
The inversion of configuration, observed during an SN2 reaction of a substrate in which the carbon atom bearing the leaving group is chiral, is known as Walden inversion.
