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Functional group

In organic chemistry functional groups are submolecular structural motifs, characterized by specific elemental composition and connectivity, that confer reactivity upon the molecule that contains them.

The following is a list of common functional groups. In the formulas, the symbols R and R' denote any group of atoms.

Chemical class Group Formula Prefix Suffix
Amines primary Amine R−NH2 amino- -amine
secondary Amine R−N(−H)−R' amino- -amine
tertiary Amine R−N(−R')−R amino- -amine
Imines primary Imine R−C(=NH)−R' imino- -imine
secondary Imine R−C(−H)=N−R' imino- -imine
Amide Amide R−C(=O)N(−H)−R' name according to the parent amine and acid, respectively: alkyl alkanamide &nbsp
Azo Azo R-N=N-R' &nbsp &nbsp
  Nitrile R−C≡N alkyl nitrile &nbsp
  Pyridyl R−C5H4N &nbsp &nbsp
Carboxylic acid Carboxyl R−C(=O)OH



hydrocarboxy- -oic acid
Alcohol Hydroxyl R−OH hydroxy- -ol
Carbonyl Aldehyde R−C(=O)H &nbsp -al
Ketone R−C(=O)−R' keto- -one
Ester Ester R−C(=O)O−R' named according to the parent alcohol and acid, respectively: alkyl alkanoate &nbsp
Ether Ether R−O−R' named according to the parent alcohols, respectively: alkylalkylether &nbsp
Alkanes Methyl R−CH3 methyl- (similarly for higher alkyl substituents: ethyl, propyl, butyl, etc.) &nbsp
Alkenes Alkene R−CH=CH−R' convert the part substituting for alk in the name of the alkane into the alk of the word alkene: ethane/ethene, propane/propene, butane/butene, etc. -ene
Alkynes Alkyne R−CC−R' convert the part substituting for alk in the name of the alkane into the alk of the word alkyne: ethane/ethyne, propane/propyne, butane/butyne, etc. -yne
Phenyl Phenyl R−C6H5 &nbsp &nbsp
  Phosphodiester R−OP(=O)2O−R' &nbsp &nbsp
Isocyantes Isocyanate R−N=C=O alkyl isocyanate &nbsp
Isothiocyanate R−N=C=S alkyl isothiocyanate &nbsp
Thiol Thiol group R−SH &nbsp -thiol
  Thioether R−S−R' &nbsp  

Combining the names of functional groups with the names of the parent alkanes generates a powerful systematic nomenclature for naming organic compounds.

The non-hydrogen atoms of functional groups are always associated with each other and with the rest of the molecule by covalent bonds. When the group of atoms is associated with the rest of the molecule primarily by ionic forces, the group is referred to more properly as a polyatomic ion or complex ion. And all of these are called radicals, by a meaning of the term radical that predates the free radical.

The first carbon after the carbon that attaches to the functional group is called the alpha carbon .

Last updated: 10-24-2004 05:10:45