Organic Chemistry - "Change", Part 3; The SN2 Reaction

Greetings,

This post covers the substitution reaction known as SN2. "S" is for substitution, "N" means nucleophilic, and "2" is for the bimolecular nature of the reaction.

A substitution reaction involves the replacement of a functional group with a new one. The reaction is nucleophilic because the substituting group attacks the carbon atom nucleus to which the original functional group is attached.  A bimolecular reaction is one for which the rate depends on the amounts of both reactants.

Explanation of the SN2 Reaction

The SN2 reaction occurs when there is a highly electronegative (high electron density) species in the vicinity of an organic molecule with an electronegative atom bonded to a carbon atom.  Here is the theoretical sequence of events:

1. An electronegative atom (such as oxygen) attacks a carbon atom bonded to another electronegative atom.
2. A temporary, short lived intermediate is formed.  This intermediate consists of both reactants bonded together and is, generally, known as a transition state.  Specifically, this transition state is known as an activated complex.
3. The original electronegative atom, bonded to the carbon atom in step 1, leaves.

The following illustration visually explains the SN2 reaction.

That is all for this post.  As always, thank you for reading!