The stereochemistry of the products of SN2 reactions are always the same as that of the reactants.
True or false?
False. The stereochemistry of the products of SN2 reactions is the opposite of that of the reactants.
True. The stereochemistry of the products of SN2 (substitution nucleophilic bimolecular) reactions are indeed always the same as that of the reactants.
To understand why, let's break down the mechanism of the SN2 reaction. In an SN2 reaction, a nucleophile replaces a leaving group in a single step, where the nucleophile attacks the electrophilic carbon atom and the leaving group simultaneously leaves. This concerted reaction results in the inversion of stereochemistry at the electrophilic carbon atom.
The reason for the inversion can be explained by the attack of the nucleophile from the backside of the electrophilic carbon, which leads to the formation of a transition state. In this transition state, the nucleophile and leaving group are partially bonded to the carbon atom simultaneously. As the nucleophile approaches from the backside, it pushes the existing groups towards the front, resulting in a flipped or inverted arrangement of groups.
Due to this backside attack and inversion of groups, the stereochemistry of the products in an SN2 reaction is opposite to that of the reactants. If the initial stereochemistry of the reactant is R (right) configuration, it will be converted to S (left) configuration in the product. Similarly, if the initial stereochemistry is S configuration, it will be converted to R configuration in the product.
Therefore, the statement that the stereochemistry of the products of SN2 reactions is always the same as that of the reactants is false.