Sandbox SN2

S_N2 reaction is a basic reaction type in organic chemistry. The letter S_N stands for nulceophilic Substitution, the number 2 stands for bimolecular, with both reactions partners are involved in the reaction rate-determining step. It also exists an S_N1 reaction; here, only one reaction partner is involved in this step. On the other side, S_N2 reactions are characterized by exchanging substituents. The substituent that leaves the molecule is called leaving group.

Typically, alkanes with a substituent in primary position undergo S_N2 reactions. In contrast to a S_N1 reaction, no stable carbo cation can be formed, therefore, another way is taken.

The S_N2 by establishing a so called intermediate state, with both educts comeing close to each other. By this, the bond of the leaving group is partly broken, and the bond to the new group is partly formed. The formation of this intermediate state is the rate determining step of the reaction. In the , the bond of the leaving group is completely broken, and at the same time the bond to the new substituent is completely formed.

The S_N2 reaction has a very interesting stereochemistry inversion of the stereocenter^[1] with an animated example of the substitution of chloride and methanol shown. Please click on the buttons below to animate the reaction with different representations. Use the popup button to enlarge the view and the quality button to turn on anti-aliasing.

The animation was originally done by Prof. Dr. Verena Pietzner; for details, see her web site ChiLe^[2]. The implementation into Proteopedia was done by Prof. Jaime Prilusky, Prof. Joel L. Sussman

and Veronika Pelekhov.