When two (especially organic) molecules approach each other, there is a possibility of several different chemical reactions, each giving different products. If the reactants collide with sufficient energy and specific orientation to form a product, then reactions occur in a single step. However, several reactions do not happen in a single step but go through multiple intermediate levels and finally lead to the products. These intermediate levels are known as transition states. Stabilisation of these transition states is very difficult because these are highly energetic and unstable species. A chemical reaction may go through many transition states and ultimately lead to a product. In a chemical reaction, the number of transition states may be different for different reaction pathways. Examples of such reaction pathways include Electrophilic reactions, Nucleophilic reactions, etc.

During these reactions, already existing bonds break and form new bonds. SN2 is one of the mechanistic pathways where one nucleophile attacks the center of another molecule and forms the product. The elimination of the leaving group and the addition of the attacking group takes place simultaneously.

This experiment aims to perform transition state calculations on the SN2 reaction between iodomethane and chloride ion.