In chemistry, a nucleophilic substitution (SN) is a class of chemical reactions in which an electron-rich chemical species (known as a nucleophile) replaces a functional group within another electron-deficient molecule (known as the electrophile). The molecule that contains the electrophile and the leaving functional group is called the substrate.[1][2]
The most general form of the reaction may be given as the following:
The electron pair (:) from the nucleophile (Nuc) attacks the substrate (R−LG) and bonds with it. Simultaneously, the leaving group (LG) departs with an electron pair. The principal product in this case is R−Nuc. The nucleophile may be electrically neutral or negatively charged, whereas the substrate is typically neutral or positively charged.
An example of nucleophilic substitution is the hydrolysis of an alkyl bromide, R-Br under basic conditions, where the attacking nucleophile is hydroxyl (OH−) and the leaving group is bromide (Br−).
Nucleophilic substitution reactions are common in organic chemistry. Nucleophiles often attack a saturated aliphatic carbon. Less often, they may attack an aromatic or unsaturated carbon.[3]
- ^ March, J. (1992). Advanced Organic Chemistry (4th ed.). New York: Wiley. ISBN 9780471601807.
- ^ R. A. Rossi, R. H. de Rossi, Aromatic Substitution by the SRN1 Mechanism, ACS Monograph Series No. 178, American Chemical Society, 1983. ISBN 0-8412-0648-1.
- ^ L. G. Wade, Organic Chemistry, 5th ed., Prentice Hall, Upper Saddle River, New Jersey, 2003.