Functional group

In chemistry, a functional group is a chain or group attached to a carbon chain, represented in the general formula by R for aliphatic compounds and as Ar for aromatic compounds, and which are responsible for the reactivity and chemical properties of organic compounds. They are always associated with covalent bonds to the rest of the molecule.

The chemical nomenclature of organic compounds is based on the combination of the prefixes (secondary function) and suffixes (main function) associated with the functional groups together with the names of the alkanes from which they are derived by accessing the atoms.

Homologous series and most common functional groups

A homologous series is a set of compounds that share the same functional group and therefore have similar properties and reactions. For example: the homologous series of primary alcohols possess an OH (hydroxyl) group on a terminal or primary carbon.

The homologous series and functional groups listed below are the most common. In the tables, the symbols R, R', or the like, can refer to a hydrocarbon chain, a hydrogen atom, or even any set of atoms.

Saturated

• Alkanes

Unsaturated

• Alkenes (methine functional group)
• Alkynes (alkynyl functional group)

Oxygen functions

Presence of some carbon-oxygen bond: single (CO) or double (C=O)

Functional group	Homologous series	Formula	Structure	Prefix	Suffix	Example
hydroxyl group	Alcohol	R-OH		hydroxy-	-ol	Ethanol
Alkoxy (or aryloxy) group	Ether	ROR'		-oxy-	R -yl R' -yl ether	Ethyl ether
carbonyl group	Aldehyde	RC(=O)H		formil-	-to the-carbaldehyde	Ethanal
Ketone	RC(=O)-R'		oxo-	-one	propanone
carboxyl group	Carboxylic acid	R-COOH		carboxy-	-ic acid	Acetic acid
acyl group	Ester	R-COO-R'		-yloxycarbonyl-	R' - yl R - ate	Ethyl acetate

For the nomenclature of these functional groups, see Nomenclature of organic functions with oxygen.

Nitrogenous functions

Amides, amines, nitro compounds, Nitriles. Presence of carbon-nitrogen bonds: CN, C=N or C≡N

Functional group	compound type	Formula	Structure	Prefix	Suffix	Example
amino group	Amine	R-NH 2		Not me-	-Not me	Isobutylamine
imine	RNCH 2		_	_
aminoand carbonyl groups	Amide	R-CO-NR 2		_	-amide	acetamide
imide	RC(=O)N(-R')-R"		_	_	Tetramethylethyldiimide
nitro group	nitro compound	R-NO 2		nitro-	_	nitropropane
nitrile group	nitrile or cyanide	R-CN		cyano-	-nitrile
isocyanide	R-NC		alkyl isocyanide	_	Tert-butyl isocyanide
isocyanate	R-NCO		alkyl isocyanate	_
isothiocyanate	R-NCS		alkyl isothiocyanate
azo group	azo derivative	RN=NR'		azo-	-diazene
Diazo derivative	R=N=N		diazo-	_	Diazomethane
azide	RN 3		azido-	-azide
diazonium salt	XRN ≡N _		_	...ide of...-diazonium
_	hydrazine	R 1 R 2 N-NR 3 R 4		_	-hydrazine
_	hydroxylamine	-NOH		_	-hydroxylamine

Halogenated functions

Composed of carbon, hydrogen and halogens.

Functional group	compound type	compound formula	Prefix
halide group	halide	RX	halo-	_
acyl group	acid halide	R-COX	Haloformil-	-oil halide

Sulfur-containing groups

Functional group	compound type	compound formula	Prefix	Suffix
sulfide group	thioether or sulfide	RSR'	alkylthio-
R-SH	thiol		mercapto-	-thiol
R-SO-R'	Sulfoxide	_	_	_
R-SO 2 -R'	Sulfone	_	_	_
_	sulfonic acid	RSO 3H _	sulfo-	-sulfonic acid

Organophosphates

Functional group	compound type	Formula	Structure	Prefix	Suffix	Example
	sodium phosphinate	PR 3		_		_
	P(=O) R3		_	_
	phosphinite	P(OR)R 2		_	_
	phosphinate	P(=O)(OR)R 2		_	_
	phosphonite	P (OR) 2R		_	_
	Phosphonate	P(=O)(OR) 2 R		_	_
	Phosphite	Q(OR) 3		_	phosphite
Phosphate group	Phosphate	P(=O)(OH) 2R		_	_
	phosphorane	PR 5		_	_