Substitution (chemistry)

Substitution in the context of organic chemistry has the general meaning of replacing an atom, a functional group, or a substituent in a molecule.

Substituted compounds
Substituted compounds are chemical compounds where one or more hydrogen atoms of a core structure have been replaced with a functional group like alkyl, hydroxy, or halogen.

Example
Benzene is a simple aromatic ring. Substituted benzenes are a heterogeneous group of chemicals with a wide spectrum of uses and properties:
 * benzene C6H6
 * toluene C6H5-CH3
 * xylene C6H4(-CH3)2
 * mesitylene C6H3(-CH3)3
 * phenol C6H5-OH
 * aniline C6H5-NH2
 * chlorobenzene C6H5-Cl
 * nitrobenzene C6H5-NO2
 * benzoic acid C6H5-COOH
 * picric acid C6H2(-OH)(-NO2)3
 * trinitrotoluene C6H2(-CH3)(-NO2)3
 * salicylic acid C6H4(-OH)(-COOH)
 * acetylsalicylic acid C6H4(-O-C(=O)-CH3)(-COOH)
 * paracetamol C6H4(-NH-C(=O)-CH3)(-OH)
 * phenacetin C6H4(-NH-C(=O)-CH3)(-O-CH2-CH3)

Substitution reaction
A substitution reaction is a general type of organic reaction where one functional group or substituent in the reactant molecule is replaced by another. Common types of substitution reactions are:
 * nucleophilic substitution.
 * halogenation

Substitution (kemi) Supstitucija (kemija) Reazione di sostituzione Substitutiereactie Substituutio