Nucleophilic substitution

In chemistry, nucleophilic substitution is a class of substitution reaction in which a electron-rich nucleophile attacks a molecule and replaces a group or atom, called the leaving group. It is a fundamental class of reaction in organic chemistry, where the reaction occurs at a carbon centre, but nucleophilic substitutions are also well known in inorganic covalent compounds too.

Related Topics:
Chemistry - Substitution reaction - Nucleophile - Leaving group - Organic chemistry - Carbon - Inorganic - Covalent - Compounds

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

If we ignore formal charges, the most general form for the reaction may be given as

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

:Nuc: + R-LG → R-Nuc + LG:

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The electron pair (:) from the nucleophile (Nuc) attacks the substrate (R-LG) forming a new bond, while 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 alkaline conditions, where the attacking nucleophile is the OH− and the leaving group is Br-.

Related Topics:
Alkyl - Bromide - OH⁻ - Leaving group

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

:R-Br + OH− → R-OH + Br−

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Nucleophilic substitution reactions are commonplace in organic chemistry, and they can be broadly categorised as taking place at an aliphatic (saturated) carbon or at (less often) an aromatic or other unsaturated carbon centre.{{Ref|1}}

Related Topics:
Aliphatic - Saturated - Aromatic

~ ~ ~ ~ ~ ~ ~ ~ ~ ~